I don't know if this problem was already reported, but searching the forum returned no appropriate results.
clients: OE 5/6, TheBAT! 2.x
Usage of web-clients is not honored in our organization, pop3/smtp are mandatory.
Sometimes when relatively large (2+ meg or so) file is attached, then only headers and few first words of message are downloaded via POP3. Regardless of mail-client software.
But in web-accessible mailbox the message (before POP3-deletion) is in perfect state, with all attachments visible and downloadable.
Right now I found only one workaround:
1. let mail-client leave POP-downloaded messages on the server for next 7 days.
2. Should above mentioned problem arose, then user may read his message via web.
But it is not good solution.