Some notifications email are not received, although they seem to be actually sent

60 r27138

I have configured email settings, using an unauthenticated and without TLS server (smtp.deckpoint.ch), and using an authenticated and using TLS server (smtp.gmail.com)

In both cases:
_ If I click on "test settings" button in admin center, I well receive an email
_ when an email should be sent due to workflow event or subscribtion, an email seems to be sent (regarding logs), but I receive nothing.

I have activated debug mode, and compared the details of e-mail server communication, but found no explanation. (See test_settings.log and Workflow.log)