But you said you moved to a new server??
That would mean that the master email account would need to be recreated.
And the smtp server name may be different on the new server also.
But anyway if you read the note in the control panel:
Use specified SMTP Server:
Normally this is controlled by php.ini. However if you need to send mail through another SMTP server and cannot do this by editing php.ini, you can specify it here.
