We have a Thunderbird client that when downloading some emails with attachments times out and after beginning to download the email. The email is held on Microsoft Exchange online and shows perfectly in the web browser interface of exchange so I know the email is OK online. I have upgraded Thunderbird to the latest version with no effect on this problem. Thunderbird is configured to download from outlook.office365.com using port 993. I have tried an inbox repair by right clicking on the inbox, selecting properties and selecting "repair" but this has no effect. The email with the attachments still times out. Can you suggest anything else to try?