POP or IMAP ? Are you only downloading headers or full copies? Do you have a restriction in the 'Disc Space' where you do not download messages larger than 64kb?

re: The sender will say "in the attachment" and I don't see an attachment. Sometimes I see the attachment but it wont open, saying that it is corrupted That sounds like you have an Anti-Virus product scanning incoming emails.

Start computer in 'Safe Mode with Networking'. Start Thunderbird. If imap then allow folders to synchronise. Check emails.

Using IMAP and downloading full copies. Most messages with attachments - at 300kb or more are fine - just occasional ones limit to 64kb. Restarted in safe+networking and reloaded mail - no difference. Same messages still show as 64kb. Checked on the webmail interface and the same message is 324k and I can see and open the attachment. I want to keep using Thunderbird but it makes it awkward to have to use something else just for occasional messages that are cropped.

Open Tools/Options/Advanced/General/Config. editor and double-click the preference mail.server.default.fetch_by_chunks to false, OK to close Options, and restart TB to see if attachments are no longer truncated.

See Problems section here.

sfhowes - You got it! Modified the config file to false - then went in to that folder and did a "folder repair" which I guess does a complete reload of the messages. 64bk messages without attachments appeared back at full size. Thanks.