…active mode (bobvandevijver)

This PR was squashed before being merged into the 5.4 branch.

Discussion
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[Mailer] Fix sendmail transport failure handling and interactive mode

| Q             | A
| ------------- | ---
| Branch?       | 5.4
| Bug fix?      | yes
| New feature?  | no <!-- please update src/**/CHANGELOG.md files -->
| Deprecations? | no <!-- please update UPGRADE-*.md and src/**/CHANGELOG.md files -->
| Issues        | Fix #54532 <!-- prefix each issue number with "Fix #", no need to create an issue if none exists, explain below instead -->
| License       | MIT

#54239 introduced an issue for us when using sendmail in interactive mode using a long running background worker. It will throw exceptions due to an unclean shutdown in case of an SMTP timeout (5 minute by default), while in interactive mode all output is actually handled by the SMTP transport, including that timeout. That makes the exit code of the long running process not relevant in that mode. See the bug report for some more details.

I have verified that this change solves my production issues, although I am not particularly fond on the hoops I had to jump to show this in the test.

cc `@aboks`

Commits
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1b2ead35ca [Mailer] Fix sendmail transport failure handling and interactive mode

* 5.4:
  [Mailer] Fix sendmail transport failure handling and interactive mode
  [Security] reviewed Romanian translation of key 20

* 6.4:
  [Mailer] Fix sendmail transport failure handling and interactive mode
  [Security] reviewed Romanian translation of key 20

* 7.0:
  [Mailer] Fix sendmail transport failure handling and interactive mode
  [Security] reviewed Romanian translation of key 20