Allow to disable gravatar
It should be possible to disable gravatar for privacy and legal reasons. (Actually it should be off by default.) You might consider to completely drop gravatar support. At least I cannot see any reason for any kind of avatar in Postorius.
As a workaround I've set GRAVATAR_SECURE_URL
to ''
in settings. This leads to relative (not existing) paths in the img src attribute instead of full URLs.