Why does Connect And Verify say Could not connect?

Read the rest of the message

After Could not connect: the form shows the reason your mail server or the connection gave. The common ones:

• Invalid login followed by your provider's reply: your username or password was refused. Check that SMTP username is your full email address. For Gmail and Outlook, create an app password in your email account's security settings and paste that into SMTP password (app password for Gmail/Outlook).
• Connection timeout or Greeting never received: nothing answered on that host and port. Check the spelling of SMTP host, then try the other common port (587 or 465).
• A message containing ENOTFOUND: the host name does not exist, which usually means a typo in SMTP host.

The form keeps what you typed, so you only need to correct the wrong field and click Connect And Verify again. The check only signs in; it never sends a test email.

Other messages on the same form

• Host, port (25, 465, 587 or 2525), username, and password are required. appears when SMTP host, SMTP username or the password is blank, or the Port is not one of the four listed. Look for an empty field first.
• Enter a valid from address. means From email is not a complete email address.
• Mailbox limit reached (10). means you already have 10 mailboxes connected. Click Remove on one you no longer use, then connect the new one.

If it connected but later stopped sending

A mailbox that passed this check can still fail later, for example after you change its password with your provider. After 3 failed sends in a row it is marked PAUSED (repeated failures). See Why is my mailbox marked PAUSED, and how do I pause or remove one myself?