My ISP modified recently the domain for its mail server from smtp.mailserver.com to out.mailserver.com

Alas, when I try to configure the outgoing mail server in Vtiger with the new domain it returns me the error message:

Mail could not be sent to the admin user. Please check the admin emailid/Server settings

Using smtp.mailserver.com is accepted although no mail is sent since that domain no longer valid.

I also tried using the IP address instead - to no avail..returned the same error..