BT have caused a right royal fuss over the weekend by blocking non-BT address on their outgoing SMTP servers. Phil Gyford has good coverage of the hurdles required to get through BT’s aggressive blocking, which is intended to combat spam by restricting mail-outs to legitimate and authenticated addresses only.
It’s a real faff, but I’m sure I’ve been through this before. In fact, at least two clients of mine have – over a year ago – encountered exactly the same problem, but everything I read regards this as a completely new update. To the best of my knowledge, one was on business-grade ADSL and the other on residential, but both had the same problem (and remedy – harass BT with copies of domain registrations and letterheads).
So I’m slightly miffed … is this a new extension of a previous BT filtering system or something completely different?