David Hunt asked,
| ... [W]ould it be unreasonable for me to use exitcode 75 to return
| the mail to the queue, then unset HOST?
Now, procmail's -t option and setting EXITCODE are things with which I have
no experience. The procmail(1) man page says there is a risk with requeuing
that the mailqueue can fill up.
Does that mean that the system mailqueue can fill up because
[1] mail for the user who requeues keeps coming back into the queue, and
after several days of requeuing, one user's accumulated mail can fill
the queue; or
[2] when a message is requeued, it still takes up its original place in
the queue because it hasn't been delivered, plus it takes up an addi-
tional slot for its requeued position, and one message requeued enough
times can fill the queue by itself?
If #2 is the case, requeuing is a lot more dangerous than it is if #1 is true.
If a user requeues ten messages a day and each one is retried every ten
minutes, then under #1, after four days the repeatedly requeued messages are
occupying forty slots in the mailqueue; under #2, gad, I hate to think, since
the oldest of those messages is using 1440 slots alone.
I have no experience with requeuing because both the ISP's where I have
accounts use Smail instead of a decent MTA.
<rant>
Smail ignores the exit status of a command to which mail is fed by a pipe in
the aliases file or in a .forward. As long as Smail can fork sh to read the
pipe, Smail considers the message delivered. If the command in the pipe
doesn't save the message or cannot be run or doesn't exist, the message is
lost and Smail couldn't give a rat's rump. (To be honest, I'm not sure if
Smail even cares about successfully forking sh before it washes its paws of
mail for an address that expands to a pipe.)
Including "||exit 75" in one's .forward is likewise pointless with Smail;
it pays no attention.
With Smail setting EXITCODE to anything nonzero is no different from setting
it to zero, and procmail's -t option has no effect, so I have no experience
with the results of requeuing under an unbroken MTA.
</rant>