MailCore/mailcore2 — pull request #944 by robario (2014-10-28 11:15:34+00:00)
Title: Add support to SMTP check account without from

We need only login check and `MAIL FROM` check is unnecessary.
Some SMTP server rejects multi `MAIL FROM`, accepts only once.
So, `checkAccountOperationWithFrom:@"example@example.com"` then `sendOperationWithData:data` is rejected.

If you want `MCOSMTPSession#checkAccountOperation` instead of `MCOSMTPSession#checkAccountOperationWithFrom:nil`, I will send another pull-request to do that.