Redmine

Redmine 4.0.x uses ActiveMailer to send emails asynchronously. In my configuration, I am also using ActiveJob::QueueAdapters::AsyncAdapter.

On my server, I am facing the odd situation that, when notifying the projects users, the initial emails are rendered and sent within about 100ms. However, after 8-10 emails, ActiveJob reports a series of email delivery problems because the execution has expired (after 30sec each). Unfortunately, I am not able to figure out (a) what causes the timeout (the Redmine server or the Mail server?) and (b) how to modify the 30sec timeout value.

In any case, it would be very helpful if Redmine didn't drop emails that cannot be delivered instantly but instead makes a retry after a certain period of time. (Imagine that a mail server may be offline temporarily!)

Does anyone have an idea on how to implement such a "retry-after-x-seconds" approach? Thanks in advance!