[NBLUG/talk] top output help

S. Saunders sms at sonic.net
Wed Apr 25 14:45:05 PDT 2007

The one bit I can answer off the top of my head is:

> If I shut down sendmail and then restart it will mail that was sent
> during the time it was shut down go out?

Depends on the "mailclient" (formally a "Mail User Agent" or MUA), and
possibly your network architecture (if that's relevant, i.e. if sendmail
acts as a network mailgate, or standalone for that box).

Some MUA's will activate sendmail (or their designated "Mail Transfer
Agent," or MTA) for the single message they are sending, rather than as a
"daemon" or service:  sendmail will start, accept the message from the MUA
and attempt to send it on to the destination MTA, then shut down (without
checking the queue, or accepting incoming messages).  If the destination
MTA issued an error, it will return that to your sender; if the
destination MTA wasn't up, it will queue the message.

Other MUA's will queue their own mail up when they can't contact a MTA.

Sendmail (and all other MTA's I know of) will automatically examine their
own queues of unsent messages, when starting, and continue their attempts
to deliver.  I believe this downtime still counts against the total
hold-queue time, however, e.g. if your sendmail only queue's for 2 days
before issuing a "permanent failure" and you shutdown sendmail for a day,
then it only tries to deliver for a day before giving up permanently...

Of the self-queuing MUA's, most default to attempting to contact the
server periodically, but IIRC I've a few times run across some that, by
default, had to be kicked off by hand.

- Steve S.
  (at least, I presume things STILL work that way, it's been some years
since I delved into sendmail that often; that's how it USED to work...

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