you can edit them out of your mail preference file, which is home/library/preferences/com.apple.mail.plist
just to be safe, make a copy of the plist file in case you mess things up and want to return to all the settings you had without reinputting them all....
you should be able to open the file with textedit, then look for a section called <key>DeliveryAccounts</key> and you'll see an entry for each of the outgoing mail servers.....delete the ones you don't use anymore.