Sending queue blocked in case of any unsendable message

[julianhofmann]

There are different reasons why a message from the queue cannot be sent:

• Incorrect mail configuration (Sending queue blocked indefinitely: Symfony Mailer throws SMTP error '550 recipient domain may not exist' #137)
• Unauthorised sender addresses
• Newsletter pages not yet published (in combination with content publisher or similar)

The task hangs as soon as a message from the queue cannot be sent successfully. And on the next run, this error-causing entry is again taken from the queue and an attempt is made to send it - again with the same error.....

Solution
The queue should have the possibility to skip erroneous entries.

One idea would be to count up a counter and ignore such entries after X faulty attempts.
However, this should not happen silently, but the sender should also be informed. One possibility would be to expand the dispatch status accordingly (not yet sent/successful/erroneous) and to display it in different colors in the status bar (similar to what Solr indexing does).

[julianhofmann]

@einpraegsam, is there a chance to get this back-ported in v17 (TYPO3 v10)?