Sending Email using IP Address instead of Domain Name

I am trying to avoid running through DNS servers to get an email message to an address on one of my hosted virtual accounts.

I know I can surround the IP address with square brackets but how do I designate the mailbox username for the (virtual) hosted account on the server?

In other words,

• I have multiple domains hosted on a virtual server -- all sharing the same IP address
• obviously, user@domain.com работает нормально
• , но как отправить пользователю @[123.456.78.90]

Возможно ли то, что я хочу сделать?

Спасибо.