[cobalt-users] 501 EMail Error

[Ezinez@xxxxxxx]

When my colleague sends an email to me from his work place, he gets the email returned with the following message:

>----- The following addresses had permanent fatal 
>errors -----
> <me@xxxxxxxxxxxxxx>
> 
> ----- Transcript of session follows -----
> .... while talking to mail.mydomain.co.uk.:
> >>> MAIL From:<him@xxxxxxxxxxxxx> SIZE=449 RET=FULL
> <<< 501 <peter@xxxxxxxxx>... Sender domain must exist
> 501 <me@xxxxxxxxxxxxxx>... Data format error

Any ideas as to why this could be.  I can send to myself from my college account and so can my other colleagues.

Thanks in advance,
L.