Unable to connect to SMPT server for Apple Mail or Airmail.

I can connect to the IMAP server in Apple Mail and in Airmail but cannot connect to the SMTP server in either app and am therefore unable to send mail. I have tried, deleting my iCloud account in Apple Mail, resetting my router, resetting the PRAM, fsck check in safe mode all to no avail. Connection Doctor does not even show the SMTP server in the panel. Incidentally, I can receive mail OK but sending is impossible. However, using iCloud.com, I can receive and send mail in Safari but this means that I can do no formatting in the body of the email. This problem is happening on my MBA as well as my 27"iMac so it seems to be a router problem which I am unable to resolve.

I I have tried to attach screenshots that may help in diagnosing the problem but I can seem only to add one at a time. There are seven screenshots in total. The password in the screenshot below has been removed and I was in the clear in the original screenshot.

I will try to upload the other screens separately in the hope that this might help resolve the issue. Thank you in advance for our help.