Invalid Email when updating existing email password
I've seen lots of similar questions about this topic but nothing that addresses this specific issue.
I have a long standing email account in my iPhone which has been working fine up to now. I finally changed the password after putting it off for too long and am now hitting a brick wall (not literally... yet).
I am able to go to the Email Account settings and pull up my details. I show a Password in the Incoming Server section and make my update there. When saving, I get an error message saying - Invalid Email Address: Please enter a valid email address for this account.
Again this is an already established account, the email address is valid. It's also NOT my primary Apple Email address. In fact, I changed that one yesterday and had no issues. Any suggestions?
iPhone SE