I did some testing:
In old Duplicati - 2.0.3.5_canary_2018-04-13 with selfigned mail certificate and with
--accept-specified-ssl-hash=
mails works (in web gui)
Also I just tested new 2.0.3.12_canary_2018-10-23 with same selfigned cert and it’ works with--accept-any-ssl-certificate=true
I’m using --send-mail-url=smtp://server:465?starttls=always
Selfigned cert is instaled in trusted root in Windows
(I did not test CommandLine version)