Issue Summary

Incoming email handler unable to retrieve large attachments from Microsoft 365 mailbox

Steps to Reproduce

1. Set up an incoming mail server using a Microsoft 365 mailbox
2. Create a mail handler using default settings using the recently created incoming email server.
3. Send an email that does not exceed 25MB in size and with an attachment bigger than 12 MB.

Expected Results

Email handler to create a new issue and add the attachment if the email size does not exceed 25MB

Actual Results

The issue gets created from the email but if the attachment is bigger than 12MB, the attachment is not added to the issue, and the flowing exception is seen in the logs:

Error while reading attachment, resulting file was incomplete and has been removed.
     stack: java.io.IOException: Error while reading attachment, resulting file was incomplete and has been removed.

Caused by: java.io.IOException: Error while reading attachment, resulting file was incomplete and has been removed.
Caused by: com.sun.mail.util.FolderClosedIOException 

Workaround

1. Configure your Mail Handler to use the Default Cloud Mail Server 
2. OR contact Microsoft to know if the timeout for reading mails can be increased.
3. Set up auto-forwarding from Microsoft 365 mailbox to Default Cloud Mail Server address and set up mail handler to use Default Cloud Mail Server.