On Mon, Jan 25, 2010 at 11:54:37PM -0500, Andrew Nady wrote:
> Is it possible to provide email service with postfix for a single
> domain that spans on multiple mailservers?
Yes. If you choose a single Internet-facing domain for geographically
diverse organization, you must arrange for internal forwarding of email
to the right destination. A user's public email address is then different
from the internal mailbox address, and your internal mail systems forward
mail as necessary from one internal cluster of mail servers to another,
possibly on a different continent.
> At location A I have 300 users and at location B 400 users. (Total
> 700 users) > These locations are geographically in different countries.
> The users are AD based and each location has a postfix mail-gateway that
> performs an ldap query.
> How could I deliver email or probe location A or B for existence
> of user_...@domain.com?
You implement the external domain as a virtual alias domain, and rewrite
recipient addresses to underlying mailbox domains that are only known
internally.
us...@example.com us...@a.example.com
us...@example.com us...@b.example.com
The mail servers at sites "A" and "B" must recognize both "us...@example.com"
and "us...@a.example.com" as being address of the same user. Each site
delivers its own users locally, but forwards mail to the remote site
(perhaps via secure-channel TLS, or a VPN, ...) when the recipient's mailbox
domain is remote.
Mail user agents, directory services, ... are configured to only work
with "example.com" and are unaware of what the mail servers are doing
behind the scenes.
--
Viktor.
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