I've suddenly found out that I've been not getting emails for the last few days if they have attachments. But this is only if they're sent to my domain address, which forwards them to my MobileMe account. So who's responsible for this problem? No way to tell yet - is it MobileMe, or is it the email forwarding? (Or is it something to do with my ISP, whose emails service I'm not actually using, but who provides the broadband? - nah...)

Apple Support are looking into it at their end. My Domain service provider is at Buddhafield Festival for the next few days, so I'm frantically emailing people to tell them to use my me.com address.

By the way, the Apple Support chat system is way better than phone support - quicker to get to talk to someone online, and I can be doing other stuff at the same time while they're checking things at their end.

Simplify the setup by temporarily stopping the forwarding, do the attachments then make it to your domain email? That will help narrow it down.

I would suspect that the attachments are not being forwarded.

My domain support guy (who is on another iPhone in a field in Somerset at the moment) thinks it's possible the server is not deleting messages after the get forwarded and so has got full up. We won't be able to confirm this for a few days as he's away, and my mac is in getting a newxairport card and SuperDrive - I can't log into the server control panel from my phone.

If you can't get to the control panel, you should be able to log on to your domain mail using its webmail function through Safari, it would show you there if it's full or not, and allow you to delete old email. Most domain emails are just mail.yourdomain.com (or .net or whatever the suffix is.) In mine I have the ability to turn forwarding on through web mail and choose to delete from the server.

Yeah, but all my login details and password etc. are on my mac - still, I get that back tomorrow. Meanwhile, all the missing emails showed up at once (some 2 days after they were sent) so I may never get to find out what the bottleneck was. The one email that was supposed to have come a week ago I realised may be a 'cheque is in the post' situation, i.e. never actually sent!

If you were receiving your MobileMe emails but none from the domain I'd blame the mail servers that handle your domain mail, not Mobile me. If it keeps happening I'd switch web hosts when you get a chance if they can't pinpoint the problem.