Linkcheck:
> Thank you for your response, Wietse. Apologies for the delay in my
> reply. I read the document you suggested and noted the possible scenario
> but cannot ascribe it to this situation.
>
> I have been finding out a bit more about the problem.
>
> The sender and his son have been getting problems when sending some
> attachments. A 13K pdf was delivered without error, images from 100K to
> 1M and above are usually stopped on the first attempt with the error
> mentioned. Further immediate attempts (several seconds delay only) to
> send the message seem to succeed on a second or third attempt.
Data corruption errors are difficult to diagnose. The solution is
to replace components one by one until the faulty component is
identified. That includes hosts and the network path between them.
For example if hostA+pathB+hostC fails reliably, but hostA+pathX+hostC
succeeds reliably, then that suggests that the problem is in
hostA+pathB or in pathB+hostC.
> The messages originate from three different computers, all recent ubuntu
> OS, all in the same house. The router is zyxel - several years old and
> never updated but I can find nothing to suggest this may be the culprit.
> The messages go over talktalk broadband on port 587 to my server.
>
> The same attachments sent using the talktalk mail server are accepted
> first try.
>
> None of my other customers has a problem sending attachments. I sent one
> to this sender with 4 20M pictures with no problem.
I suppose those other customers have other network providers.
If that is the case, then I speculate that talktalk is preventing
their customers from sending large email messages directly, and
requires that talktalk customers send through the talktalk server
instead. This is a fairly common malware countermeasure.
Wietse
