Gmail – Send Mail As – Not Receiving Mail

I’m struggling to set up a Gmail account to send as and receive as a different email. Right now, I can ‘send mail as’, but for no apparent reason, the email refuses to receive anything sent to it.

Details:

  • This is a separate non-gmail account (it’s a cPanel/dovecot account), and it’s not set up via G Suite.
  • I know for fact that emails are making it to the first email account because I’m logged in via Thunderbird (which was the only way to confirm access anyhow).
  • The server is in the form secureXXX.servconfig.com.
  • I was able to get ‘Check email from another account’ to work, but this is not what I want, as it’s extremely delayed.

Am I forgetting something? Using the wrong ports? etc.
And are there no ‘Incoming Server’ options for Gmail’s ‘send as’ config?