Go to the Official manager of the Official mailserver and let him check your settings (in Outlook Express) and his settings (in his mail server).
Maybe there's an Official helpdesk positioned in between, but you don't tell about the Official procedures, and I can't guess that.
I configured my Official mail on the outlook express, it is receiving fine, but it is not sending mail to other email addresses except to my colleagues' Official email addresses which is almost the same as mine except for their names.
But from our website, I can use this same Official email address to send mails to any email address.
Please assist on what to do to solve the problem.