Crash when clicking Save button in attachments view

I cannot reproduce this. Have you enabled sending crash reports in the Software Update preferences pane and have you set a contact name? (This makes it easier for me to find related crash reports.)

Does it happen for all emails?

Does it happen if you first save the attachment using a different method and then click the save button?

Have you enabled sending crash reports in the Software Update preferences pane

Yes.

and have you set a contact name? (This makes it easier for me to find related crash reports.)

I hadn't, but did now.

Does it happen for all emails?

Yes.

Does it happen if you first save the attachment using a different method and then click the save button?

Yes.

I saved the crash log and will send that via e-mail, as Lighthouse says “Upload Quota Reached.”

Ok, it appears MailMate fails a bit too hard on not being able to create a folder. Could you launch MailMate from a Terminal window and then let me know what the output is when it crashes. You can launch it like this:

/Applications/MailMate.app/Contents/MacOS/MailMate

(I'd like to confirm that the folder is related to the issue.)

Thanks, that helped me to find the error myself. Here's the output:

Warning: Unable to handle alternative in multipart of MIME type:
'text/calendar' Warning: Unable to handle alternative in multipart of
MIME type: 'text/calendar' 2021-05-05 10:16:15.299
MailMate[67257:792557] Fatal: Unexpectedly unable to create folder
(file:///Users/oldusername/Downloads/). Error
Domain=NSCocoaErrorDomain Code=513 "You don’t have permission to save
the file “Downloads” in the folder “oldusername”."
UserInfo={NSFilePath=/Users/oldusername/Downloads,
NSUnderlyingError=0x12375a200 {Error Domain=NSPOSIXErrorDomain Code=13
"Permission denied"}} fish: Job 1, '/Applications/MailMate.app/Cont…'
terminated by signal SIGABRT (Abort)

The relevant part here is that MailMate is trying to save the attachment in the Downloads folder of an obsolete user account (oldusername) that no longer exists on this machine.

I had set the Downloads folder in the General preferences years ago on another Mac, but usually use the Messages > Save Attachments command, which opens a file selection dialog, so I hadn't noticed until recently, when I tried using the new(ish) Save button in the attachments view.

Changing the Default Downloads Folder in the preferences to point to the folder in my current user account solves the problem.

Not sure if you could avoid this by writing the user account path as ~ in the preferences file, instead of the absolute path.

But in any case, this was a problem with my configuration, and not really a bug, so feel free to close this issue as resolved or invalid.

Thanks for helping me to find the cause.