After many updates I just tried to see the settings of this plugin. The settings were unclear so I thought I could just disable and dispose the plugin. That tended to disable my outgoing mail at all.
As the settings were not showing it was unclear what the right settings were, so I couldn’t just override the settings with new ones and decided to downgrade to try to see the settings.
No luck, even deleting the mail_bank* – tables and deleting the plugin made things worse. Reinstalling the plugin gave an even more corrupted settings-pane with an error-message.
I just used a backup of the mail_bank-tables to revive the plugin and then put in some new settings. Only after overwriting these invisible but successful settings the settings-panes now work right, even with the newest version. The settingspanes, however remain not quite intuitive for retrieving current settings as they are only visible in the ‘3 step scenario’ which is meant for altering them.