Comment # 6 on bug 1039471 from Sebastian Ernst

My initial working configuration, which works:

ernst@e7:~> rpm -qa | grep -i thunder
MozillaThunderbird-translations-common-45.8.0-39.1.x86_64
MozillaThunderbird-45.8.0-39.1.x86_64
ernst@e7:~> rpm -qa | grep -i enigmail
enigmail-1.9.5-1.4.x86_64
ernst@e7:~> rpm -qa | grep -i kmozilla
ernst@e7:~> rpm -qa | grep -i mozilla-kde
mozilla-kde4-integration-0.6.4-8.3.x86_64

First test, regular update of Thunderbird (not from the maintenance queue) -
saving encrypted attachments to disk is broken:

ernst@e7:~> rpm -qa | grep -i thunder
MozillaThunderbird-52.1.0-41.3.1.x86_64
MozillaThunderbird-translations-common-52.1.0-41.3.1.x86_64

Second test, having removed mozilla-kde4-integration, it's still broken:

ernst@e7:~> rpm -qa | grep -i mozilla-kde
ernst@e7:~>

Third test, Thunderbird and Enigmail from the maintenance queue,
mozilla-kde4-integration removed, and it's still broken:

ernst@e7:~> rpm -qa | grep -i thunder
MozillaThunderbird-52.1.1-41.6.1.x86_64
MozillaThunderbird-translations-common-52.1.1-41.6.1.x86_64
ernst@e7:~> rpm -qa | grep -i enigmail
enigmail-1.9.7-2.3.1.x86_64
ernst@e7:~> rpm -qa | grep -i mozilla-kde
ernst@e7:~> 

Reverting everything back to the initial configuration, and it works as
expected. It's not the KDE integration, as far as I can see.