Hi,

We've a hosting account for example.com with web hosting company, with 3 locations sharing the same domain name.

At location 1, we have L1user1@example.com, L1user2@example.com etc. If I send mail to L2user1@example.com it returns

550 5.1.1 <L2user1@example.com>: Recipient address rejected: User unknown in virtual alias table


I've tried

/etc/postfix/main.cf:

virtual_alias_maps = hash:/etc/postfix/virtual
virtual_alias_domains = example.com
transport_maps = hash:/etc/postfix/transport
relay_host = smtp.somewebhostingcompany.com

/etc/postfix/transport:

example.com relay:[smtp.somewebhostingcompany.com]

/etc/postfix/virtual:

L1user1@example.com L1user1.localvirtual
L1user2@example.com L1user2.localvirtual


What i'd like to achieve is whenever L1user1 sending emails to (anyone)@example.com it will be relayed to smtp.somewebhostingcompany.com whenever the user is not found in local virtual table.

Thanks.

Regards,
Adam

It doesn't work like that.
Either a domain is local (meaning local delivery is attempted) or it is not (meaning mail is relayed to the server responsible for that domain).

You probably want to use subdomains (user@sub1.domain.com, user@sub2.domain.com) so mail can be routed to the correct server, with a single server handling the head domain.
You can also use aliases and address rewriting to achieve your user@domain.com addresses to be used both internally and externally, but you want to plan it out carefully as these setups can get messy and confusing very quickly.

hmmmm ok then, thanks for the quick reply. Guess i'll have to figure some other way out.

Probably set up one of the servers to be the MX host for domain.com, with a virtual alias table mapping all the user@domain.com to their respective user@sub.domain.com addresses (it can also be a sub.domain.com host).

Each of the sub's should also have an alias table for the local users (local1@domain.com -> local1@sub.domain.com) so "in house" mail doesn't need to go out to the domain.com server and back.

Keeping the local and master lists in sync is an extra maintenance task though.