Ok so, if you are able to fetch the IMAP folder, that means the settings are all right, otherwise, there may be something missing..
If you can fetch the IMAP folders (for income settings) without problem AND the SMTP settings are the ones as above, but you cannot send emails, check if this email account is your default, if it is not, set it as default and try sending an email now. If you do not wish to set it as default, check how many emails accounts do you have and when you prepare a new email message ready to be sent, click on "From" and check where are you sending the email from...
If that doesn't help, check out at the Admin Panel, in your Cron Settings, if you have chosen to send the emails through Cron. If you have, you must set up your Cron correctly in order to send the emails, otherwise, they will never go out. Check
this thread, last page, to see how to run the Cron.
Greetings!