Having spent days trying to get my work email to send after getting O2 Broadband, a solution emerged from their excellent Twitter customer service.
From a ton of internet stalking, I knew it was something to do with the SMTP service being blocked according to a load of reading but none of the solutions out there worked for me.
So I turned to Twitter and it looks like adding “relay.o2broadband.co.uk” was the solution. Seeing as I didn’t see this info out there anywhere else during my search, thought I would get this up for any of you other desperate people with an outbox clogged with despair.
Hope it helps!