Allow overriding smtplib local_hostname

[David Nolan]

Hey all.

In cloud environments, when using django.core.mail.backends.smtp.EmailBackend, socket.getfqdn() is called to resolve the 'reported hostname' for smtplib. This often resolves to an internal DNS name, not the intended name.

It would be convenient to provide a kwarg to allow overriding this setting, which is currently hard-coded in the open() function.

See https://github.com/django/django/blob/master/django/core/mail/backends/smtp.py#L53

I’m happy to create a ticket for this but the contribution guidelines advise emailing the list first.

[Tim Graham]

Hi, there's already a ticket: https://code.djangoproject.com/ticket/6989