Mail send button is greyed out

[alainr]

I am running 10.11.6 el capitan on my mac.
I usually use gmail on chrome to send mail, but i needed to send something via MAIL and the send button is now greyed out.
usually it works. Mail shows the most recent emails i send and received using GMAIL, but i can't send now using Mail.
In preferences, the incoming server info is blank.
the outgoing mail server: gmail is selected
TLS certficate None port 993

any suggestions? what do i do?

 

[BleverCastard]

Set up your inbound server details.