I am having the similar difficulty, of Outlook 2003 not sending messages I create. I choose send on the message itself and it goes to my Outbox. I did make a note of that different what I have seen previous to, messages that have not been sent are in italics, but the ones at the present are not. I choose send or receive and get the dialogue box which shows sending and receiving, but the message remains in outbox, and it not sent. I have no inaccuracy messages, no restrictions by ISP, no connectivity problems, as I do receive email which was sent by additional public.
Bookmarks