By default tests are expected to produce no assertion. This also updates the existing tests to match.
The git-send-email [0] script uses StartTLS if `smtpEncryption` is set to `tls`, which can break services that don't support StartTLS. [0]: bd42bbe1a4/git-send-email.perl (L1533) PR #1395
bd42bbe1a4/git-send-email.perl (L1533)
This will allow, e.g., the character `@` in the email identity. Also adds a test case. Fixes #557