Can't send emails to other servers, error message Sending of the message failed. The message could not be sent because the connection to Outgoing server (SMTP)

Can receive emails fine and can also send emails to the same server. Can't send to any other servers such as gmail, indeedemail, etc. Error message says 'Sending of the message failed. The message could not be sent because the connection to Outgoing server (SMTP) mail.numberfit.com timed out. Try again' Have tried changing port, but this hasn't worked so far.