Mails that got stuck in sending (e.g. SMTP timeout) will get recovered
and sent on the next flush.

refs KIME-3340

Mails that got stuck in sending (e.g. SMTP timeout) will get recovered
and sent on the next flush.

refs KIME-3340

Only log to Debug in case no mails are sent, so that the log does not
get swamped.

refs KIME-3340

The limits can be set in the settings file. It prevents the application
reaching some limits set by the mail server.

refs KIME-3340

refs KIME-3340

Initial commit that overrides the Neos SwiftMailer package with a
spooler and adds a command to send the messages from the queue.

refs KIME-3340