Corrupt Office Attachments

It seems to be a connectivity issue. Have you monitored the network traffic. Are there any dropped packets during transmission. Many times the connection to a server is lost. But somehow this is treated as an 'End of transmission' by the mail client, which is errorneous. It sounds that way.

It would be a poor pop3 client if it behaved as RanjeetRain said i.e. treating TCP connection failure as end of message. There are lots of people who use POP3 over dial-up and constantly get cut-off mid message without having partial deliveries of attachments. POP3 uses TCP so, unless their TCP/IP stack has a severe defect, has built-in error detection and correction. The POP3 client will never see or notice dropped or corrupt packets. You do not say what your email client is - Outlook Express? - or is is an automated popper?

I presume that you have checked at both the sending, the hosting and receiving computers there is no shortage of disc space or user quota :-)) and that your users are not doing something awful like two of them downloading the same account simultaneously (though that should be locked if the server knows what it is doing)?

If you are able to exercise control at the SENDING end, then ask the senders to include themselves (or some other test victim such as you personally) on the dist list for all messages and make sure that THEY get the attachments intact. That will eliminate the SENDING client end (e.g. sending a file, not complete).
Alternatively (or as well if you are inclined):
I am unfamiliar with Outlook, but on Eudora it is easy to set it up so that it "collects" mail, but also leaves it on the server i.e. collect but do not delete. {Select "persona", "properties", "incoming mail" and check box "leave mail on server"}.
If there is a corrupt attachment, then on the client it is possible to ask for a re-download (once again, Eudora {Right click on little green triangle per message "change server status" to "fetch" which can be repeated as often as you like}). Alternatively you can use another mail client on the same account to see if the second download of the same mail is corrupt (maybe the victims can phone you to carry that out). This will eliminate all the path up to the pop3 server (but not the server itself). Of course your server disc will fill and you will have to clear out maybe each evening, but that is no big deal during experimenting.
At the receiving client end a potential culprit is a virus checker interfering with the POP3 temporary files (remember that pop3 messages come as one huge message which the client chops up into text, various attachments etc. Make sure that any temporary directory used by the mail client is not subject to virus scanning.

If you have not fixed your problem, then give more details including results of some tests above and I will try to help.

Sanktwo,

Have you used OE? You would experience a lot of things if you use it.

And I am sure the asker would know if he is running out of disk space.

I have only used OE extremely briefly (at work). Since I was responsible for a huge installed park of computers I know precisely what I would experience - worms, trojans, viruses :-))  . Despite the fact that the recommended email client was Eudora, many people in the company insisted on using Outlook. Because of its integration and automation in Windows, together with the fact that it validated peoples email address by loading images from the internet unasked (I know that on the very latest versions that can now be disabled), it caused a huge cost load, split between cleaning up the viruses and dealing with the millions of spam messages. So, whilst I am pretty familiar with POP and smtp, OE I cannot help with. However, even I cannot bring myself to believe that it is so bad as to treat a tcp errored termination as successful end of message in POP transactions; surely not! Is that what you are saying?
How about you with Eudora?

I spent a little lesser time with Eudora than you did with OE :))

We're using Outlook 2000. Unfortunately this is an  intermittant problem and we don't have enough disk space on the pop3 server to leave messages on the server. I have some users that will get 70+ mb/day in attachments. However, it seems to only occur from a particular smtp server. To date, all the corrupt attachments have been sent through this hosted smtp server. Also, it hasn't happened for almost a week. Guess I'll wait for another occurance.

You have answered lots of questions yourself so you must know the value of getting concrete information those trying to help you. I am not sure what more information you will gain by simply waiting for the next ocurrence of the failure.

Obviously, I am suspicious of any system that runs at the limits of its disc space; applications have been known to behave oddly when faced with failure to write to disc. At around 1$ per gigabyte, mebbe adding some disc space to permit experimenting (and perhaps solve the problem) might be no bad thing - do you have a pointy-haired boss blocking that? Somebody is paying for your time to worry about this problem, might be cheaper to add disc first, then see if it continues.

Next, you say "from one smtp server". I guess this means that you must at least have a chain:
[Client] -> [smtp server 1] -\
[Client] -> [smtp server 2] -> [smtp receiver+pop server] -> [O2000] client
[Client] -> [smtp server 3] -/
(for example to permit virus scanning)
and and you are accusing one of the smtp servers in this chain (rather than the link [smtp receiver+pop server] -> [O2000] client ) do I have the correct story, and if not, what is it?

As I said before, the server is hosted by our ISP. For a small office, I can't justify the $9000 we'd need for enterprise exchange (to handle the massive amount of email we get). We have a (online) disk quota of 200 MB for 20 users. This is for mail waiting to be downloaded. It's not a factor of running out of space. We're talking about a quota, not a limit. However, if I were to have everybody leave the mail on the server for a week, we'd blow that quota 10X over. ISPs get a little twitchy about that. I can do it for one or two users, but the problem occurs too infrequently and randomly.

The last corrupt attachment was sent from a user in the office to another user in the same office. It went out to a hosted smtp server (mail.megapath.net). Then was received by the hosted pop3 server. After being downloaded, the attachment was corrupt (missing 100 bytes). When resent 5 minutes later, it came through the same chain and was clean.

As far as waiting for the problem to reoccur being a viable option: a sonicwall pro we had moved to that office recently was acting up with certain attachments. Emails with PDF attachments would just hang forever half way through the download. After disabling its email filtering, that issue seems to be solved. It's possible that the attachments were being corrupted by the filter as the problem hasn't occured since then. There's definately something wrong with the PRO's 6.5.0.4 firmware and email filtering. Unfortunately, they don't seem to be updating the firmware for Pro's any more.

Mrpez1:  You have very good reason to wait to see if it will happen again having removed a facility already failing on other attachments. I understand your comment on quota versus hard limit from my experiences with computer bureaux many years ago. SMTP and pop I can manage but I have no idea about how the content filtering works in the sonicwall pro. Best of luck.

As I've  not had any more corrupt attachments, I'm assuming the Pro's email filtering was at fault. I think I solved it myself.