Linux – Delayed email, server side using dovecot/postfix

email-serverlinuxpostfix

Alternative title: How to delay a mail queue in postfix for a certain user.

I am planning to build a solution. At first it would be I would create a separate email address for queuing. Use a client to send the email from that address. The queue on that email would be paused (not processing) and then create a job/script or something(separate question) to relay a sendmail -q to postfix to release the queue.

How do I make the queue stay in a delayed state so this is possible. I do not wish to stop the service and restart it at certain times since that would disable all other email.

Best Answer

You could instruct postfix via header_checks to hold emails with specific subjects or headers and then have a cron job that would release those emails at specific intervals/time.

So you would put this in your postfix configuration:

header_checks = regexp:/etc/postfix/header_checks

and then create the header_checks file an put:

/^From: "snailmail/ HOLD

then a cronjob would have to scan the mails that are on hold and release them.

Related Solutions

Postfix relaying : email to multiple addresses with one relay

The maximum number of recipient per mail is fixed by the parameter smtp_destination_recipient_limit and the default value is 50.

You can check your configuration by running :

# postconf | grep smtp_destination_recipient_limit

Linux – How to rate-limit outgoing email on Linux/Postfix host

I gave up on using postfix to solve this problem. Instead, I found a relatively clean way to solve the problem using MH, which is the mailer I have been using for over 15 years:

An outgoing mail that should be delayed by N hours is composed in the MH "draft folder" +delayN.
When I have finished composing the mail, to ensure that I leave the mail in the folder instead of sending it, I have a modified whatnow program that treats send as a synonym for quit if the message is stored in a folder whose name has the form delayNNN, where NNN is a nonempty sequence of digits.

My hourly cron job checks all relevant folders and ships files that are old enough (details elided):

for path in $MAIL/delay*[0-9]
do
  minutes=...
  for outgoing in $(find $path -mmin +$minutes -name '[0-9]*')
  do
    folder=... 
    msg=...
    send -draftfolder +$folder -draftmessage $msg
  done
done

Best Answer

Related Solutions

Postfix relaying : email to multiple addresses with one relay

Linux – How to rate-limit outgoing email on Linux/Postfix host

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