Email reports are not sent


not all mail reports are sent. The process aborts with the following message:
WARNING [2021-05-03 01:21:44] 2328 /app/dbplanet/int/apache-2.4-inst1/htdocs/piwik/libs/Zend/Mail/Protocol/Abstract.php(324): Warning - fwrite(): SSL: Broken pipe - Matomo 3.14.1 - Please report this message in the Matomo forums: (please do a search first as it might have been reported already)

We use a self-hosted SMTP server.
Sending probably always stops when the server starts to swap.

What can we do?



Matomo 3 uses a quite old and sometimes weird library for sending E-Mails. So my main recommendation would be to update to Matomo 4 which replaces it with PHPMailer which works far better and can give better error messages.

Apart from that it seems like the connection to the SMTP server is aborted, so maybe the other end (so the error logs of the mail server) might help.