In oups.com,
tezarin typed:
Thanks for your message. Sorry for not putting all the info, that was
my first post here. I am trying to investigate that problem for one
of my co-workers: she uses Outlook 2003, SP1. No mode was found there.

She hasthis problem when she sends an email to 3 clients of hers and
that's it. I am getting no error myself and sent email to other
people with no problem.

thanks in advance

Try creating a new mail profile for her, then. You still haven't included
info on the kind of e-mail account(s) she uses, though.