On Mon, 1 Apr 2002, Walter Co wrote:
> Sorry but this question is not Linux related..but this is the best place
> that I know to post this inquiry..why is it that we cannot send out emails
> with attachments, the smtp always returns a timeout error but if the email
> has no attachment, it goes out ok. According to the Destiny support people
> they do not have this problem. Guys, perhaps some tips or pointers. Thank
> you in advance and sorry for this off topic post.
this sounds familiar and the possible explanation is TCP/IP related
and so sounds complicated. i found a good explanation under
http://www.postfix.org/faq.html. scroll down to the section labelled
IP Path MTU Discovery.
basically, it's like this: mail attachments are usually delivered in
very large packets. each such big packet has the warning sign "Dont
chop me to little bits of smaller packets". when such packet passes
through a router that must do some mandatory chopping, it drops the
packet, *but* politely signals your computer (via an ICMP packet similar
to 'ping') to resend them again but in smaller packets. that ICMP packet
signal should have done the trick but it didnt because it was
blocked/firewalled along the way going back to your machine. so your
computer never got the chance to resend mail in smaller packets which in
turn translates to a timeout on your mail client.
only destiny and you can verify this problem. if this is, then fix the
router or the firewall blocking the above packets.
pong
_
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