Reinstalling won't help to change that setting back to what it was.
What I should do: delete the account and enter it again, just as you did the first time. Should work.
But let me share a story.
Last month, a friend of mine who used Windows Live Mail had switched ISP's and needed to implement the new email address. It worked already with her husband who used Thunderbird (another email client), so it couldn't be difficult.
- The intermediate result was that she could receive mail from her new ISP, but not send mail.
- The end result (after a few hours) was that I had installed Thunderbird and migrated her contacts and mail from WLM to Thunderbird. Indeed, that worked.
A bottle of wine is not the best pay you can imagine for a few hours of work. But that's what friends are for.
I hope your experiences will be better.