+++ This bug was initially created as a clone of Bug #1710220 +++

Two types of temporary attachment files remain in the tmp folder after sending

1. when editing a draft/template that contains attachments, tmp files are created by mimedrft.cpp
2. when attaching public key to a message, a tmp file (key.asc) is created by nsMsgComposeSecure.cpp

Before bug 1710220, they were removed by MimePart.jsm, but that is the cause of 1710220.

This problem also exists when using nsMsgSend.cpp, but we will only fix the new js backend.

Pushed by mkmelin@iki.fi:
https://hg.mozilla.org/comm-central/rev/03ce93477849
Remove temporary attachment files when closing compose window. r=mkmelin

Just a general comment: There is nsIExternalHelperAppService.deleteTemporaryFileOnExit()
https://searchfox.org/comm-central/search?q=deleteTemporaryFileOnExit&path=&case=false&regexp=false

Comment on attachment 9221263 [details]
Bug 1710323 - Remove temporary attachment files when closing compose window. r=mkmelin

[Approval Request Comment]
Regression caused by (bug #): bug 1211292
User impact if declined: Temporary attachment files are not cleaned up after sending
Testing completed (on c-c, etc.): c-c
Risk to taking this patch (and alternatives if risky): low

Comment on attachment 9221263 [details]
Bug 1710323 - Remove temporary attachment files when closing compose window. r=mkmelin

[Triage Comment]
Approved for beta

Thunderbird 89.0b4:
https://hg.mozilla.org/releases/comm-beta/rev/f63edfde70ef