When it reaches a limit, the mail is returned with an error message, most likely the victim of an aliasing loop. The hop count is incremented every time the mail is processed. Relay (gateway) submission of a message, e.g., when rmail calls sendmail. Otherwise, an "X-Authentication-Warning" header is added to the message. f should only be used by "trusted" users (normally root, daemon, and network) or if the person you are trying to become is the same as the person you are. The envelope sender address is used as the recipient for delivery status notifications and may also appear in a "Return-Path:" header. This address may also be used in the "From:" header if that header is missing during initial submission. Sets the name of the "from" person (i.e., the envelope sender of the mail).
![mail command in linux mail command in linux](https://image.slidesharecdn.com/mail-20services-20and-20mail-20commands-20in-20linux-130619123418-phpapp01/85/mail-services-and-mail-commands-in-linux-33-320.jpg)
Most other categories are only useful with, and documented in, sendmail's source code. The option -d0.1 prints the version of sendmail and the options used during the compile. A list of numeric debugging categories found in the TRACEFLAGS file in the sendmail source distribution. More than one flag can be specified by separating them with commas. Higher levels generally mean more output. The category is either an integer or a name specifying the topic, and level an integer specifying the level of debugging output desired. Set the debugging flag for category to level. Send debugging output to the indicated log file instead of stdout. sendmail gives up any enhanced ( set-user-ID or set-group-ID) privileges if an alternate configuration file is specified. Verify mode is normally used for validating users or mailing lists. Verify names only do not try to collect or deliver a message. This mode reads addresses and shows the steps in parsing it is used for debugging configuration tables. This flag implies all the operations of the -ba flag that are compatible with SMTP.
![mail command in linux mail command in linux](https://www.tecmint.com/wp-content/uploads/2014/12/Install-Postfix-in-Ubuntu.png)
Use the SMTP protocol as described in RFC 821 on standard input and output. Print number of entries in the queue(s) only available with shared memory support. Purge expired entries from the persistent host status database. Print the persistent host status database. Same as -bd, except it runs in foreground. sendmail will fork and run in background listening on socket 25 for incoming SMTP connections. Also, the "From:" and "Sender:" fields are examined for the name of the sender. All input lines must end with a CR- LF, and all messages will be generated with a CR-LF at the end. Current legal values are 7BIT or 8BITMIME. Use sendmail.cf even if the operation mode indicates an initial mail submission. Use submit.cf even if the operation mode does not indicate an initial mail submission. newaliases mailq hoststat purgestat smtpd Sendmail can also be invoked, with special functionality, using the following commands. Beginning with version 8.10, the sender is included in any alias expansions for example, if "john" sends mail to "group", and "group" includes "john" in the expansion, then the letter also delivers to "john". Aliasing can be prevented by preceding the address with a backslash.
![mail command in linux mail command in linux](https://i.ytimg.com/vi/GILLpadIhYg/maxresdefault.jpg)
Local addresses are looked up in a file and aliased appropriately. It determines the network(s) to use based on the syntax and contents of the addresses. With no flags specified, sendmail reads its standard input up to an end-of-file or a line consisting only of a single dot, and sends a copy of the message found there to all of the addresses listed. sendmail is used only to deliver pre-formatted messages. Sendmail is not intended as a user interface routine other programs provide user-friendly front ends. sendmail does internetwork forwarding as necessary to deliver the message to the correct place. Sendmail sends a message to one or more recipients, routing the message over whatever networks are necessary.