Ok, yes that's a really old version of Android and we're actually only supporting version 2.3.3 onwards. I did check with an old phone we have in the office and it's giving me the same error as well, when it used to work ok. I think it might be something to do with the fact our servers are a bit overloaded and we're adding more tonight
Thanks for the answer, Nick, even though I was hoping for something different. ;-(
I'll try again after work tonight, but as the phone is working OK and I don't plan on replacing it, I will just have to make do with washing mail from my laptop when I've got home, instead of on the move...