It seems like the mail here is the correct one. If trying to backup through /admin/backups and you have self host, is it supposed to work?
Sidekiq/retries shows many posts with the following:
Jobs::HandledExceptionWrapper: Wrapped Net::OpenTimeout: execution expired
It also shows this one:
Jobs::HandledExceptionWrapper: Wrapped Net::SMTPAuthenticationError: 535 Incorrect authentication data