SMTP not working with Outlook 2016

This answer doesn't help all those who are having the same problem.  Thats what FORUMs are used for....

I was having the same kind of issues.  First I was getting the box asking for my user name and password.  Next I could not send mail with my outlook 2016.  I tried my cox webmail and had no issues getting or sending mail.  Tech support confirmed all my settings were correct and advised me to use webmail until they fixed the smtp server.  Today I exported my mail to a pst file and removed the account. Changed my password for my cox account and added my cox mail account back to outlook -- reviewed the settings and they were the same as before, so I imported my mail pst file and restored all my saved mail.  Now I can send and receive mail.   we will see for how long.  I hope I do not have to go thru all this again

Something is going on.  Whenever I get the SMPT error, I know Cox is having server troubles.  The first 5 times it happened (over the years)  i did all of the normal troubleshooting.  nothing helped. eventually Cox would get it fixed.  for a while they transferred me from the servers in the western USA to the eastern servers.  February 18 I could not send emails. I get a dialog box with the choice to "Try Later" or "Edit Message".  I choose Edit and keep trying until it sends.  Cox said they were going to post a Current Issues page on their website; I am going to check if anything has been posted.  That would save countless hours of rebooting computers, clearing caches, deleting cookies. (all of the normal suggestions which never help).