Add SMTP_HELLO_NAME to let operators set the EHLO/HELO identity

Google Workspace SMTP relay (smtp-relay.gmail.com) rejects generic
EHLO identifiers such as "localhost", which is Go net/smtp's default.
Operators can now set SMTP_HELLO_NAME to a valid hostname so that
c.Hello() is called before StartTLS, satisfying strict relay policies.

Fixes https://github.com/getprobo/probo/issues/1284

Signed-off-by: Bryan Frimin <bryan@probo.com>

pkg/probod/probod.go

@@ -654,6 +654,7 @@ func (impl *Implm) Run(
 			User:        impl.cfg.Notifications.Mailer.SMTP.User,
 			Password:    impl.cfg.Notifications.Mailer.SMTP.Password,
 			TLSRequired: impl.cfg.Notifications.Mailer.SMTP.TLSRequired,
+			HelloName:   impl.cfg.Notifications.Mailer.SMTP.HelloName,
 		},
 		l.Named("sending-worker"),
 		[]mailer.SendingWorkerOption{