Can't sign in message. Android mail app

my ISP (Talktalk) recently asked me to change my password for my Tiscali email address. I changed the password in the Android Mail App (yellow icon) on my Nexus 5 and I can send and receive emails ok. however, every time I go into the App for this address I see the message "Can't sign In". everything seems to be working fine though so I am not sure the relevance of this message of what I do to get rid of it. Any ideas?

I get this occasionally with my Yahoo account. As you note, things seem to work fine, and the message usually goes away fine when I dismiss it. A bit annoying, but doesn't seem to be an issue.

Ditto with Yahoo