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Tue, Sep 27, 2016 11:05 pm

Daily testing of email deliveries using mailx

I needed a way to perform a daily check that a Linux email server is able to successfully transmit email to external email addresses. Such a test can easily be scheduled using cron and mailx. You can use the crontab utility to schedule mailx to run periodically and send a test message to a specified email address. E.g., the following entry will send a test message at five minutes after noon every day to

05 12 * * * mailx -s "Daily email delivery test" </home/jan/Documents/daily_mail_test_message.txt

The body of the message will contain the contents of the file /home/jan/Documents/daily_mail_test_message.txt.

The first 5 elements on the line in the crontab file are scheduling elements:

 # ┌───────────── min (0 - 59)
 # │ ┌────────────── hour (0 - 23)
 # │ │ ┌─────────────── day of month (1 - 31)
 # │ │ │ ┌──────────────── month (1 - 12)
 # │ │ │ │ ┌───────────────── day of week (0 - 6) (0 to 6 are Sunday to
 # │ │ │ │ │                  Saturday, or use names; 7 is also Sunday)
 # │ │ │ │ │
 # │ │ │ │ │
 # * * * * *  command to execute

If an asterisk is used for an element, that indicates that scheduling is done for every possible value for that element. E.g., the 05 on the line indicates five minutes after the hour, in this case 12 (noon) and the following three asterisks indicate that the cron job should be run every day of every month and every day of the week, i.e., Sunday to Saturday.

[ More Info ]

[/network/email/mailx] permanent link

Fri, Apr 10, 2015 10:37 pm

Sending messages and files with mailx

On a Linux/Unix system or OS X system, a very quick way to send email messages and files by email from a shell prompt, aka command line, is to use the mailx utility.

If you wish to send the contents of a file as the body of a message, you can use a command like the following one:

$ mailx <report.txt

The above command would send the contents of the file report.txt to The contents would be inserted within the body of the message. In the above case, the message would have no subject. You can use the -s option to the command to provide a subject for the message. E.g.:

$ mailx -s "Just a test" <report.txt

The above command would send the same message as the previous one, but this time with a subject line of "Just a test". If the subject line contains a space, you must enclose the subject within quotes.

If, instead of sending a file's contents in the body of the message, you wish to send it as an attchment, you can use the -a option on Linux/Unix systems, but not on OS X, since the -a option isn't supported for mailx for that operating system.

$ mailx -s "another test" -a report.txt -b,
A test message with an attachment.
Also sending to two BCC email addresses

In the above example, the file report.txt is sent as an attachment to the message with used as the "to" address. I also sent the message to two additional addresses as blind carbon copy (BCC) addreses using the -b option. When using the -b option to send to multiple email addresses, separate the addresses with a comma. Instead of putting the contents of the file report.txt in the body, the body in the above example consists of the two lines starting with "A test message". You can provide the body of the message by simply typing the mailx command line then hitting return and then starting typing whatever you want to appear in the body of the message. When you are finished, hit Ctrl-D, i.e., the Ctrl and D keys simultaneously. You will then see EOT appear for the end of text and the message will be transmitted.

If you wish to put email addresses in the carbon copy (CC) field, use -c, instead of -b. As with the -b option, separate multiple email addresses with a comma.

If you wish to see if the message has been transmitted from the sending system, you can use the mailq command. If it hasn't been transmitted you will see the message still in the queue as in the example below from a Mac OS X system.

$ mailq
-Queue ID- --Size-- ----Arrival Time---- -Sender/Recipient-------
AEADBD2536AA*     370 Fri Apr 10 22:10:44  jsmith@GSOD000962737L.local

On a Linux/Unix system, you will need to run the mailq command as root or you can run the command with sudo, if the account you are using is in the sudoers file.

Though, if the message isn't shown in the queue, there still could have been a failed delivery attempt. E.g., a short time after issuing the mailq command above on a OS X system, when I reissued the command I saw the following indicating the system could not send the email via mailx.

$ mailq
postqueue: fatal: Queue report unavailable - mail system is down

[/network/email/mailx] permanent link

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