Client has the 2003 version of Outlook (11.5608.5606) and is having problems
on the laptop.

First, are there any updates to this version we should try?

When trying to do work in Outlook 2003, the error "The messaging interface
has returned an unknown error. If the problem persists, try restarting
Outlook."

Well, yeah, the problem persists! Restarting Outlook sometimes helps,
sometimes not.

This version is supposed to be able to handle large .pst files. Their inbox
lists as 3.5 Gb, and the next largest is the sent folder at 286 Mb.

Recently, incoming email appears multiple times in their inbox. IOW, the
same email is repeated in the inbox.

Thx.

--
Bill