> >How many seconds will Imail wait before it thinks the remote mail
> >server is unavailable and place the mail message into the queue? 30
> >seconds? 60 seconds? And where can I change this value?
>
Actually, I do not have any direct information on this timeout period, but
yes, it would be reasonably short, on the order of a minute or 2. The way to
check would be to look in a log file for a 'MX connect Fail' message and
trace that sequence back from the time IMail writes the delivery status, to
its beginning to see the time between the connection attempt and the error
msg. I don't have a log with this info right now, so cannot say. Also note
that your assumption is that IMail will place the message right back into
the Queue, but if the remote site has multiple MX records, the connection
attempt will be tried to each MX host and finally to the IP for the 'domain
name' before this will occur. All these timeouts could add up to many
minutes. Sorry, there is no way that I know, to change this timeout.
> If there is no initial repsonse to an SMTP call, the timeout could be
> quite short, but once an SMTP session is going, the timeouts are much
> longer, I bet.
Yes, this too is true, Len. Once an incoming connection is made to the SMTP
service, IMail will keep it open for something like 15-20 minutes, even
though no traffic is observed. No reason not to expect that an outbound
connection would also remain open as long as needed to deliver the data, or
until some other response or action from the remote, caused IMail to close
it or a timeout occurs. If the remote host disconnects for some reason, that
usually will cause IMail to also close its end of the connection (remember
those PTR lookup responses from Sendmail servers and IMails re-actions?).
> >My problem is that the Firewall that my Imail server is behind is SLOW!!!
> >and things are getting stuck in the queue when they probably should be
> >getting sent out.
>
Just because you FW is slow, should not cause any great effects. IMail can
work with dialup connections, so slow data rates (up to a point!) should not
have any real effects. Of course, it the data rate is less than a couple
Kb/Sec, then things could get dicey!
Note that failed delivery to outside hosts, is often caused by DNS related
problems. The DNS IMail is using may not be providing responses, or
providing incorrect responses, so IMail cannot make the connection. Network
routing issues can also have similiar effects. Can you, from the IMail
machine, using telnet, on port 25, connect to an external mail server (Len's
or Ipswitch's)? If you cannot do that, than IMail will not be able to make
it SMTP connection, either. Try by name and by IP. If IP works but name does
not, then DNS is the problem. If neither work, then you have more basic
network problems.
> If you're sure that's the case, then shorten the Imail SMTP retry
> period to 5 minutes so when Imail does timeout, it will retry fairly
> soon, on the assumption that the firewall might just let the mail
> through next time, or next time, or next time.
I'm not so sure this is a good idea. If the connection is not succesful on
the first attempt, why would a second or third attempt have a better chance
of success? If the timeouts work out to be longer than your Queue Timer
setting (with multiple MX attempts, timeouts and failures), IMail will see
that this message is still in process and not attempt delivery of it again
until after it finishes this attempt and the Queue timer goes off again. If
one does assume the second connection will be made (DNS and other connection
related data is now cached in the firewall, so it will be faster?), then the
start of the second attempt, needs to be before the cached data expires and
for DNS data, that is usually measured in hours or days, so a small change
from 30 to 10 minutes is not likely to 'miss' the cached data. Also if you
do have lots of messages in the Queue, you could cause IMail to reach its 30
SMTP deliver processes, rather quickly and keep it at the max for long
periods of time. This would not speed up delivery. BTW, the minimum setting
for the Queue Timer is still 10 minutes, even though it may look like you
can set it below this value.
Daniel Donnelly
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>
> Len
>
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