Displaying decrypted e-mails

[leonbotros]

After decryption, the displayed folder switches to the Postguard Received folder, however the e-mail is not selected and shown.

[leonbotros]

Setting the selected message will be possible soon via (mailTabs.setSelectedMessages()):
https://bugzilla.mozilla.org/show_bug.cgi?id=1786711

Also copying/creating messages without an experiment will be possible soon:
via messages.import(): https://bugzilla.mozilla.org/show_bug.cgi?id=1646473