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I am trying to familiarize myself with crontab. I know that it is supposed to send an email containing the output of jobs to the user that scheduled them however, I can see in the syslog that the address crontab is sending emails to is not a "local" one (as if I were to type mail -s "email here" username) but an external email address (like [email protected]).

Can someone tell me from where this email is derived and how I can set the users' email address to something else?

This could be because I have a top-level domain associated with my instance (I can see in the log the emails are being sent there), however, I actually have two domain names pointed to this server so I don't know how crontab is choosing or what would happen if there were no domain on this machine.

In short I am just trying to figure out where this default email address is set.

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  • On what operating system? The capabilities to send emails to non-local users depends on the cron implementation. And what MTA (mail server software, e.g. postfix, exim, etc.) are you using? It may be the MTA that's doing the rewriting.
    – Gilles 'SO- stop being evil'
    Commented Aug 17, 2016 at 21:47
  • This is for Ubuntu Linux. What is strange to me is that, until I installed mailutils, I could not even use the mail program, therefore I do not know how cron would have sent an email (even to local users).
    – Startec
    Commented Aug 18, 2016 at 5:05

2 Answers 2

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man 5 crontab

       If MAILTO is defined (and non-empty), mail  is  sent
       to the user so named.  MAILTO may also be used to direct mail to multi‐
       ple recipients by separating recipient users with a comma.
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  • 2
    Good find! Unfortunately this does not explain where mail is sent if MAILTO is not defined and does not answer my question.
    – Startec
    Commented Aug 17, 2016 at 4:43
  • 4
    user@cat /etc/mailname or how you configured your mta. it's not crontab's job to choose address, it always addresses the local user.
    – Ipor Sircer
    Commented Aug 17, 2016 at 4:47
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    Ah, there is the answer I am looking for. So it appends the users' name onto how the mta was configured. I see, thank you.
    – Startec
    Commented Aug 17, 2016 at 4:50
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POSIX specifies that output should be mailed, but not how, so the answer is implementation-dependent, and there are unfortunately numerous cron implementations. If you aren't sure which cron daemon package you use, try the manual page for the crontab file: man 5 crontab

Vixie Cron

The most influential implementation is Paul Vixie's, which offers MAILTO. In Debian 11 and Ubuntu up to 23.10, the manpage of Vixie Cron reads:

If MAILTO is defined (and non-empty), mail is sent to the user so named. MAILTO may also be used to direct mail to multiple recipients by separating recipient users with a comma. If MAILTO is defined but empty (MAILTO=""), no mail will be sent. Otherwise mail is sent to the owner of the crontab.

Example

MAILTO="[email protected],[email protected]"

Manual pages

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