A780 Email error:"Invalid recipient address"

[Yongyut]

I get the above error when sending mail.
My mail server settings are correct because they work on another device.
No matter if I enter the email address manually or from the phonebook:The phone connects to the mail server and then pops up this error and the mail is not sent.I can receive POP3 mail normally though.
I also called Motorola customer support (Thailand) but they don't know anything (they suggested to reset the device, eventually even reflash it with the same firmware).It looks like a problem with the A780.
Has anybody experienced the same problem or what could be the cause of it?It's strange as I can receive my mail normally.

[Yongyut]

Problem solved:
At first I thought there was something wrong with my precious A780 but the problem was my ISP's mail server (CS Loxinfo) which blocks all outgoing mail from my phone company (DTAC) because it's a competitor.By the way it works with AIS as this belongs to the same company as CS Loxinfo.This is a silly game but what can we consumers do about it?Anyway I can use email now after switching to DTAC's own smtp server which is "ksc.th.com".
So this might be worth knowing for some people in Thailand.