by reggie choo.
seems that moodle's phpmailer isn't sending HELO/EHLO when relaying mails.
some SMTPs require this.
work around:
- installed postfix MTA on moodle server.
- moodle will relay to local postfix MTA (set it such that HELO/EHLO command is not required)
- postfix will then relay to other SMTP/MS-Exchange etc.
thanks.