attachments sent from iOS cannot be easily opened on Ubuntu [Roma cannot reproduce, tom to retry]

[tomholub]

4. downloaded file doesn't get recognized as a xlsx file. It does have the right extension, and it does seem to have the right contents. But maybe the mime-type is wrong / not preserved. Compare to forwarding with browser extension, which works. (issue also present on a jpeg file, and likely most others)

I tried to reproduce this issue, but .xlsx file opens well after forwarding from iOS. Maybe it happens only with some specific files, I forwarded the same message to your email, can you please check if it woraks or not for you?

The issue (missing mime type inside the encrypted enclosure) is present on all files. But the user-facing problem (can't open as a result) only manifests on some host OS, and possibly only for some file types.

I tested sending and forwarding message with 2 attachments (image and xls file) - in both cases app sends right content-types (image/jpeg and application/vnd.openxmlformats-officedocument.spreadsheetml.sheet) to Core.composeEmail function.
Then I downloaded these attachments from browser on macOS and checked mime types - they were the same as sent by the app.
So I think we should create another issue for finding why attachments mime-type is wrong on Linux OS, as it's not only for forwarded messages. May be some difference in decrypting .pgp files.

Originally posted by @sosnovsky in #1090 (comment)