What Does Your User Agent Say About You?


A user agent is a computer program representing a person, for example, a browser in a Web context.

Besides a browser, a user agent could be a bot scraping webpages, a download manager, or another app accessing the Web. Along with each request they make to the server, browsers include a self-identifying User-Agent HTTP header called a user agent (UA) string. This string often identifies the browser, its version number, and its host operating system.

Spam bots, download managers, and some browsers often send a fake UA string to announce themselves as a different client. This is known as user agent spoofing.

The user agent string can be accessed with JavaScript on the client side using the navigator.userAgent property.

A typical user agent string looks like this: "Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:35.0) Gecko/20100101 Firefox/35.0".


User Agent String

Browser Data

Linux Mail User Agent

James Lee
• Wednesday, 06 July, 2022
• 25 min read

An MTA is an application that routes and transmits electronic mail from one node on a network to another. On a network node, exists an email client that is used to send and receive messages to and from the mail server, an email client also makes use of the SMTP protocol but it is not necessarily an MTA.

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Because of its complicated configuration steps and demands, and weak security mechanisms, many new MTA have come up as alternatives to Send mail, but importantly, it offers everything to do with mail on a network. Post fix is a cross-platform, popular MTA that was designed and developed by Waits Weave Enema for his mail server while working at IBM research department.

Post fix runs on Linux, Mac OSX, Polaris and several other Unix-like operating systems. It borrows a lot of Send mail properties on the outside, but it has a totally and comprehensively distinct internal operation.

Additionally, it bids to be fast in performance with easy configurations and secure operation mechanism and has the following major features: Exit is a free MTA developed for Unix-like operating systems such as Linux, Mac OSX, Polaris and many more.

No support for POP and IMAP protocols Supports protocols such as RFC 2821 SMTP and RFC 2033 SMTP email message transport Configurations include access control lists, content scanning, encryption, routing controls among others Excellent documentation It has utilities such as Lemonade which is an assortment of SMTP and IMAP extensions to enable mobile messaging plus many more. Email is also another free, open-source and modern Linux MTA when compared to the other MTA we have looked at.

Mutt is a small yet powerful terminal based email client for Unix-like operating systems. Teaming is the fastest growing and most trusted community site for any kind of Linux Articles, Guides and Books on the web.

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Most of them respect a convention going back to Unix's early days; the contents of the environment variable VISUAL, if it exists, is taken as the name of your preferred editor. But if you are, like me, the sort who always has a GNU Emacs running, the most useful way to set EDITOR is to the value emacsclient.

The emacsclient program, when it runs, tries to establish communication with an Emacs instance you already have running and hand the mail message temporary file to that Emacs to be edited. The effect of this will be that when your mailer calls out for an editor, a mail composition window pops open inside your Emacs.

When you are ready to hand the file back to the mailer for sending, type C-x #. If you're running XEmacs rather than GNU Emacs, these directions change slightly.

It is descended from elm and has similar commands by default, but is much more powerful and configurable. It can be a POP3 or IMAP client, and includes excellent support for MIME and PGP.

Elm was the first modern, screen-oriented Unix mailer, but has been stagnant for years now and is being displaced by Mutt. For more information, see the elm sources and installation instructions in the Meta lab mail user agents directory.

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Pine is an user agent designed for novices; it includes news-reading capability and built-in support for the IMAP remote- mail protocol. I find its impoverished command set, limited configurability and native editor hard to take.

The Netscape browser has POP3 and IMAP remote- mail capability built into it, so it can be used as a mailuseragent. Netscape supplies its own mini-editor, the same one used throughout the browser (e.g. for text fields in forms).

The small mode can be quite useful, as you get to compose mail inside a full Emacs environment (but see also the discussion of emacsclient elsewhere in this document). Every time you run it, it converts your inbox to Baby format; ordinary mail tools will choke on that.

There is a mail reader for Emacs called `vm' that writes and reads standard V7 mailboxes. It is not distributed with GNU Emacs, but you can find its home page at

Mush mailuser's shell, very powerful for filtering and batch processing An MA is a program that, at a minimum, allows a user to read and compose email messages.

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Brief : In this article, we list some of the best email clients for Linux desktop. So, here is a list of best email clients available on the Linux platform.

Features: Unified Inbox : Mainspring supports all the major email providers. Calendar Integration : Mainspring will check your calendar and let you book meetings at a suitable time when you are free or send your availability schedule to others.

You can customize its look however you see fit by tweaking its CSS stylesheet or extend its features with various extensions available. Thunderbird is one of the most popular and oldest open-sourced email client from Mozilla Foundation.

Activity Manager : Recorded interactions between the email provider and Thunderbird. Customization: Thunderbird supports skins for changing the look & feel.

Evolution is an open-source email client from GNOME project. Privacy & Security : Evolution supports both PGP & S/MIME encryption.


Email is the email client part of Contact, a personal information manager, that was developed for and fits nicely with the KBE environment. Privacy & Security : Email supports PGP & S/MIME encryption.

Another variation of Gear is Pantheon Mail, that is maintained by Elementary OS community. Features: Interface : Gear is modern looking and lightweight with a simple user -interface.

Note: Gear is best suited in GNOME desktop environment or its variants. Speed is a lightweight email client that uses GTK+ interface.

Privacy & Security : It includes support for GPG encryption. Note: Needs manual configuration for email accounts except Gmail.

Claws Mail is another email client using GTK+ interface. Features: Contacts Management : It has basic address book functionality.

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Note: Needs manual configuration for email accounts. If you are an avid terminal fan, Mutt is a text-based email client.

Features: Interface : Mutt runs entirely in your terminal windows with a text-based user -interface. Customization : Highly customizable with keybindings and macros support.

Note: If you are a beginner user, you might find it difficult to configure Mutt. Despite being a promising paid app, it seems that the Hire developers have become unresponsive.

If you have a company or team, Dylan N1 or Hire, both are good choice. Thunderbird is the traditional email client and a safe bet for personal use.

In this review, we shall exclusively dive into looking at some of the best command-line email clients for Linux and the list is as follows. Please note, all these below email clients can be installed using default package managers such as yum, DNF or apt as per your Linux system distribution.

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Mutt is a small, lightweight yet powerful text-based email client for Unix-like operating systems. Mutt Email Client for Linux Alpine is a fast, easy-to-use and open-source terminal-based email client for Unix-like operating systems, based on the Pine messaging system.

Alpine also runs on Windows, can be integrated with web-based email user agents. Its development was highly influenced by Sup, and it offers performance enhancement to several Sup features.

The basic idea is to configure an offline IMAP client that allows syncing your local computer with a remote email server. User -interface designed for speed, with fast keystrokes for common actions.

Mu4e Email Client for Linux Lu mail is a console-based email client that is developed especially for GNU/ Linux with fully integrated scripting and supporting operations upon local Fielder hierarchies and remote IMAP mail -servers. There are many graphical-based email clients for Linux, but comparatively, Lu mail designed solely for command-line use only with built-in support for scripting with a real language.

It is free and open-source software which is very powerful and extensible and is perfect for discerning hackers. Arc Email Client for Linux The above-listed command-line or terminal or text-based email clients are the best you can use on your Linux system, but many times, you can only find out good features and performance attributes of an application after testing it.

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Importantly, you can also let us know of any other command-line email clients that you think deserve to appear in the list above, through the comment section below. Teaming is the fastest growing and most trusted community site for any kind of Linux Articles, Guides and Books on the web.

Nobody likes spam, and SpamAssassin is probably the best free, open source spam fighting ninja that you could hope to have in your corner. Once you’ve done that, you can see how it’s configured in the /etc/ mail /spam assassin/ file.

SpamAssassin runs a number of scripts to test how spammy an email is. The higher the score that the scripts deliver, the more chances there are that it’s spam.

In the configuration file, if the parameter required_hits is 6, this tells you that SpamAssassin will consider an email to be spam if it scores 6 or more. A 1 or a 2 means that a new report message will be created by SpamAssassin and delivered to the recipient.

A value of 1 indicates that the spam message is coded as content message/rfc822, and if it’s a 2, that means the message has been coded as text or plain content. Text or plain is less dangerous because some mail clients execute message/rfc822, which is not good if they contain any kind of malware.

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Unfortunately, SpamAssassin can’t catch everything, and spam messages can still sneak through to fill up the mailboxes on your Linux email server. But never fear because you can filter messages before they even get to the Post fix server with Mealtime Black hole Lists (BLS).

The above BLS are the most common ones found, but there are plenty more on the web for you to track down and try. Post your question in this forum. Notices Welcome to, a friendly and active Linux Community.

By joining our community you will have the ability to post topics, receive our newsletter, use the advanced search, subscribe to threads and access many other special features. Note that registered members see fewer ads, and Contenting is completely disabled once you log in.

If you have any problems with the registration process or your account login, please contact us. For more advanced trainees it can be a desktop reference, and a collection of the base knowledge needed to proceed with system and network administration.

This book contains many real life examples derived from the author's experience as a Linux system and network administrator, trainer and consultant. They hope these examples will help you to get a better understanding of the Linux system and that you feel encouraged to try out things on your own.

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Click Here to receive this Complete Guide absolutely free. All tools/categories handled by update-alternatives are listed in /var/lib/pkg/alternatives and I can't see an MA there. All times are GMT -5. is looking for people interested in writing Editorials, Articles, Reviews, and more. A web application which provides message management, composition, and reception functions may act as a web email client, and a piece of computer hardware or software whose primary or most visible role is to work as an email client may also use the term.

The common arrangement is for an email user (the client) to make an arrangement with a remote Mail Transfer Agent (MTA) server for the receipt and storage of the client's emails. The MTA, using a suitable mail delivery agent (MDA), adds email messages to a client's storage as they arrive.

The default setting on many Unix systems is for the mail server to store formatted messages in box, within the user's home directory. Of course, users of the system can log-in and run a mail client on the same computer that hosts their mailboxes; in which case, the server is not actually remote, other than in a generic sense.

The Post Office Protocol (POP) allows the user to download messages one at a time and only deletes them from the server after they have been successfully saved on local storage. However, there is no provision for flagging a specific message as seen, answered, or forwarded, thus POP is not convenient for users who access the same mail from different machines.

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IMAP provides folders and sub-folders, which can be shared among different users with possibly different access rights. IMAP features an idle extension for real-time updates, providing faster notification than polling, where long-lasting connections are feasible.

In addition, the mailbox storage can be accessed directly by programs running on the server or via shared disks. Direct access can be more efficient but is less portable as it depends on the mailbox format; it is used by some email clients, including some webmail applications.

The email clients will perform formatting according to RFC 5322 for headers and body, and MIME for non-textual content and attachments. Headers include the destination fields, To, Cc (short for Carbon copy), and BCC (Blind carbon copy), and the originator fields From which is the message's author(s), Sender in case there are more authors, and Reply-To in case responses should be addressed to a different mailbox.

To better assist the user with destination fields, many clients maintain one or more address books and/or are able to connect to an LDAP directory server. The email client is usually set up automatically to connect to the user's mail server, which is typically either an MSA or an MTA, two variations of the SMTP protocol.

Client settings require the name or IP address of the preferred outgoing mail server, the port number (25 for MTA, 587 for MSA), and the username and password for the authentication, if any. There is a non-standard port 465 for SSL encrypted SMTP sessions, that many clients and servers support for backward compatibility.

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With no encryption, much like for postcards, email activity is plainly visible by any occasional eavesdropper. Without it, anyone with network access and the right tools can monitor email and obtain login passwords.

Examples of concern include the government censorship and surveillance and fellow wireless network users such as at an Internet café. All relevant email protocols have an option to encrypt the whole session, to prevent a user's name and password from being sniffed.

They are strongly suggested for nomadic users and whenever the Internet access provider is not trusted. S/MIME employs a model based on a trusted certificate authority (CA) that signs users' public keys.

Open PGP employs a somewhat more flexible web of trust mechanism that allows users to sign one another's public keys. Header fields, including originator, recipients, and subject, remain in plain text.

In addition to email clients running on a desktop computer, there are those hosted remotely, either as part of a remote UNIX installation accessible by telnet (i.e. a shell account), or hosted on the Web. Both of these approaches have several advantages: they share an ability to send and receive email away from the user's normal base using a web browser or telnet client, thus eliminating the need to install a dedicated email client on the user's device.

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The main limitations of webmail are that user interactions are subject to the website's operating system and the general inability to download email messages and compose or work on the messages offline, although there are software packages that can integrate parts of the webmail functionality into the OS (e.g. creating messages directly from third party applications via MAPI). Like IMAP and MAPI, webmail provides for email messages to remain on the mail server.

By contrast, both IMAP and webmail keep messages on the server as their method of operating, albeit users can make local copies as they like. With limited bandwidth, access to long messages can be lengthy, unless the email client caches a local copy.

There may be privacy concerns since messages that stay on the server at all times have more chances to be casually accessed by IT personnel, unless end-to-end encryption is used. Another important standard supported by most email clients is MIME, which is used to send binary file email attachments.

Email servers and clients by convention use the TCP port numbers in the following table. For MSA, IMAP and POP3, the table reports also the labels that a client can use to query the SRV records and discover both the host name and the port number of the corresponding service.

It simply provides a warning that transmitting user credentials in clear text over insecure networks SHOULD be avoided in all scenarios as this could allow attackers to listen for this traffic and steal account data. Unlike SMTP, however, it needs authentication: Users have to identify themselves and prove they're who they claim to be.

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Unfortunately, the authentication usually consists of presenting a username and a password known only to the user and the POP3 server. Because SSL-wrapped POP3 sessions are encrypted from beginning to end, no messages, usernames, or passwords are exposed in clear text.

This solves the problem of the disclosure of reusable passwords, but does nothing to prevent eavesdroppers from reading users' mail messages as they're being retrieved.” ^ Updated Transport Layer Security (TLS) Server Identity Check Procedure for Email-Related Protocols.

In addition to providing remote shell access and command execution, OpenSSH can forward arbitrary TCP ports to the other end of your connection. This can be very handy for protecting email, web, or any other traffic you need to keep private (at least, all the way to the other end of the tunnel).

Ssh accomplishes local forwarding by binding to a local port, performing encryption, sending the encrypted data to the remote end of the ssh connection, then decrypting it and sending it to the remote host and port you specify. Now to encrypt all of your POP traffic, configure your mail client to connect to localhost port 110.

It will happily talk to mail host as if it were connected directly, except that the entire conversation will be encrypted. Clear text Considered Obsolete: Use of Transport Layer Security (TLS) for Email Submission and Access.

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You are then expected to type in your message, followed by an 'control-D' at the beginning of a line. In normal usage mail is given no arguments and checks your mail out of the post office, then prints out a one line header of each message found.

Deletion causes the mail program to forget about the message. You can use the reply command to set up a response to a message, sending it back to the person who it was from.

Text you then type in, up to an end-of-file, defines the contents of the message. While you are composing a message, mail treats lines beginning with the character ~ specially.

For instance, typing km (alone on a line) will place a copy of the current message into the response right shifting it by a tab stop (see indent prefix variable, below). Other escapes will set up subject fields, add and delete recipients to the message and allow you to escape to an editor to revise the message or to a shell to run some commands.

You can end a mail session with the quit q ) command. Messages which have been examined go to your box file unless they have been deleted in which case they are discarded.

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Unexamined messages go back to the post office. It is also possible to create a personal distribution lists so that, for instance, you can send mail to “cohorts” and have it go to a group of people.

Such lists can be defined by placing a line like alias cohorts bill oz alp AKF mark kridle@ucbcory The current list of such aliases can be displayed with the alias command in mail.

System wide distribution lists can be created by editing /etc/aliases, see aliases (5) and send mail (8); these are kept in a different syntax. System wide aliases are not expanded when the mail is sent, but any reply returned to the machine will have the system wide alias expanded as all mail goes through send mail.

Mail has a number of options which can be set in the.mail file to alter its behavior; thus “set ask cc” enables the ask cc feature. If given a numeric argument n, goes to the n PTH previous message and prints it.

Executes the shell (see sh (1) and CSH (1)) command which follows. Chdir © Changes the user is working directory to that specified, if given.

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Deleted messages will not be saved in box, nor will they be available for most other commands. Edit (e) Takes a list of messages and points the text editor at each one in turn.

With no arguments, it tells you which file you are currently reading. Hold (ho, also preserve) Takes a message list and marks each message therein to be saved in the user is system mailbox instead of in box.

This command is very handy for suppression of certain machine-generated header fields. Mail (m) Takes as argument login names and distribution group names and sends mail to those people.

This is the default action for messages if you do not have the hold option set. With an argument list, types the next matching message.

Quit (q) Terminates the session, saving all undeleted, unsaved messages in the user is box file in his login directory, preserving all messages marked with hold or preserve or never referenced in his system mailbox, and removing all other messages from his system mailbox. A return to the Shell is effected, unless the rewrite of edit file fails, in which case the user can escape with the exit command.

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Set (SE) With no arguments, prints all variable values. Quotation marks may be placed around any part of the assignment statement to quote blanks or tabs, i.e. “set indent prefix=””" saveignore is to save what ignore is to print and type.

The number of lines printed is controlled by the variable towlines and defaults to five. Unalias Takes a list of names defined by alias commands and discards the remembered groups of users.

Unset Takes a list of option names and discards their remembered values; the inverse of set. Extremely useful for such tasks as sending and receiving source program text over the message system.

You can move mail is attention forward to the next window with the z command. Here is a summary of the tilde escapes, which are used when composing messages to perform special functions.

Tilde escapes are only recognized at the beginning of lines. CD Read the file “ dead.letter from your home directory into the message.

he Invoke the text editor on the message collected so far. After the editing session is finished, you may continue appending text to the message.

oh Edit the message header fields by typing each one in turn and allowing the user to append text to the end or modify the field by using the current terminal erase and kill characters. or filename Read the named file into the message.

UV Invoke an alternate editor (defined by the VISUAL option) on the message collected so far. After you quit the editor, you may resume appending text to the end of your message.

PW filename Write the message onto the named file. If the command gives no output or terminates abnormally, retain the original text of the message.

Options are controlled via set and unset commands. Ask, ask sub Causes mail to prompt you for the subject of each message you send.

If you respond with simply a newline, no subject field will be sent. Askcc Causes you to be prompted for additional carbon copy recipients at the end of each message.

Responding with a newline indicates your satisfaction with the current list. Askbcc Causes you to be prompted for additional blind carbon copy recipients at the end of each message.

Responding with a newline indicates your satisfaction with the current list. Ignored also applies to mail command mode.

Setting this option causes the sender to be included in the group. Nosave Normally, when you abort a message with two About (erase or delete) mail copies the partial letter to the file “ dead.letter in your home directory.

Searchheaders If this option is set, then a message-list specifier in the form /x:you will expand to all messages containing the substring y in the header field x. When mail runs in verbose mode, the actual delivery of messages is displayed on the user is terminal.

PAGER Path name of the program to use in the more command or when CRT variable is set. If CRT is set without a value, then the height of the terminal screen stored in the system is used to compute the threshold (see stay (1)).

If this name begins with a /, mail considers it to be an absolute path name; otherwise, the folder directory is found relative to your home directory. The default is “box” in the user is home directory.

Indentprefix String used by the ~m tilde escape for indenting messages, in place of the normal tab character (I). Toplines If defined, gives the number of lines of a message to be printed out with the top command; normally, the first five lines are printed.

Mail utilizes the HOME, USER, SHELL, DEAD, PAGER, LISTER, EDITOR, VISUAL and Box environment variables. ~/.mail File giving initial mail commands.

Only used if the owner of the file is the user running this copy of mail. Newaliases (1), vacation (1), aliases (5), mainland (7), send mail (8) and. Rs The Mail Reference Manual.

This man page is derived from The Mail Reference Manual originally written by Kurt Shoes. I am a graduate student and a relative Linux novice.

It is on this system where your mail spool is being maintained. It really depends on how the sysadmins within a given environment choose to do so.

Slm slm314k8989 gold badges678678 silver badges795795 bronze badges Unless your machine is misconfigured, the command mail (or other mail programs such as mutt) will access your local mailbox.

If the mailbox is in a non-standard location, the system administrator may have configured the system to set the MAIL environment variable to the location of your mailbox. If you've never received mail on that machine, then the file won't exist.

You wouldn't ever interact directly with the MTA: it's something that the administrator set up. In a multiple-computer environment, it is common to configure a single machine to receive all mail.

Even if you are receiving mail locally, it's possible that it is redirected to another machine. Check if you have a file called.forward in your home directory: it contains an email address to redirect your mail to, or some other directive telling the MTA what to do when you receive mail.

You may also have a.procmailrc file if the MTA is configured to use proclaim to deliver the mail, which is fairly common. Here you should find a file called the same as your username, that is your mailbox.

Did you check to see if you have post fix as a mail transfer agent (MTA) configured? The config file for Post fix will generally have a clue.

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