Outgoing Mail not sending - icloud bot recognised as outgoing server - says 'null'

I cannot SEND mail - I get the message "Connections to the server “p35-smtp.mail.me.com” on the default ports timed out." and the screen shows the icloud mail server (which is my only mail server) as being 'null'.

My network connection is excellent. I am receiving email notifications.

I've run 'Mail Connection Doctor' and for BOTH IMAP and SMTP servers it gives the following message:

"Could not connect to the IMAP/SMTP server check your network connection and that you entered the account information in preferences (I've not changed ANYTHING in the preferences, ever) - Also verify that the servers supports SSL. If it does not, deselect the SSL box, in the Advanced tab of account preferences'.

All I want to do is send an email...! HELP!

I use a MacBook Pro late 201.13 on OS 10.12.6