I don't know if there is a button you can click to get rid of them. but here's a little more difficult way. (actually two)
This information is stored in the com.apple.mail.plist file in your ~home/Library/Preferences folder.
First thing to do, either way is to quit Mail.app and back up this file. Just copy it to the desktop or something. Now:
Way # 1:
If you have the developer tools installed, double-click the com.apple.mail.plist file in your ~home/Library/Preferences folder. That will bring up the Plist editor which will display a nested list of property/value pairs.
Click the widget next to 'root' to expand it, then click the widget next to 'DeliveryAccounts'
that will open a numbered list of accounts, you will have to click the widget next to each of the accounts to see which one they are.
With the number of the account you want to remove selected, click the delete button. repeat for all the accounts you want to remove. save the file and restart mail.
Way #2:
You DON'T have dev tools installed, or you love XML. That's fine, this way isn't much harder.
open TextEdit (or emacs if you are 1337) and then file: open the com.apple.mail.plist file. scroll down (or do a 'find' for your mail server's address) until you find what looks like the following:
Code:
<key>DeliveryAccounts</key>
<array>
<dict>
<key>AccountType</key>
<string>SMTPAccount</string>
<key>Hostname</key>
<string>smtp.yourmail.com</string>
</dict>
<dict>
<key>AccountType</key>
<string>SMTPAccount</string>
<key>Hostname</key>
<string>smtp.yourOthermail.com</string>
</dict>
</array>
ok, this is pretty easy to understand, even if you don't know xml. there is an Array called DeliveryAccounts, in it are dictionary entrys for each server, select the server(s) you want to delete, starting with the <dict> tag and ending with the </dict> tag. and hit delete.
save and relaunch mail.
of course. someone will probably post a message right after this saying "oh yeah, theres a button in this tab called..." and i'll look like a jacka$$. but whatever. Worked for me.
