mail snaffu -- what smtp port to use?

[Simon]

Ultimately, it doesn't really matter if you use your mobile provider's or IDNet's outgoing mail server, as they both achieve the same thing.

Except for one thing.  Emails from my phone, to one particular person, always get caught by his spam trap, but emails from the same address, using IDNet's SMTP server, don't, so it seems that somehow, some spam filters pick up on the O2 SMTP.   

[Sebby]

That's true. Try IDNet's - it does work with authentication!