i have upgraded to el capitan and my outgoing mail server will not go online

Greetings geofflane55,

Thanks for using the Apple Support Communities!

I understand that you are having an issue with a mail account on your Mac. It sounds like you may be unable to send messages and the account may be showing as offline. If this is the case, I would suggest reading over and working through the suggested troubleshooting steps outlined in the following article.

If you can’t send or receive email on your Mac - Apple Support

Have a great day!

Mail (El Capitan): Mail troubleshooting

Mail (El Capitan): If you can’t send messages

Mail not sending or receiving messages after updating OS X