HELP PLEASE!!! We can't receive external mail

[Dan Murray]

First Problem

We have just started using Microsoft Exchange 5.5 as our Internet Email
Server. Before we used SLMail but we had Exchange 5.0 basically just for its
folder sharing capabilities. After problems with SLMail we have upgraded
Exchange to 5.5 and installed Internet Mail Services on both of our exchange
servers. The problem we have now is that we can send mail internally and
externally but we cannot receive mail from outside.

When I try to send from a yahoo account I get the following message:

<us...@mycompany.com>:
145.142.151.96 does not like recipient.
Remote host said: 550 Unable to relay for us...@mycompany.com
Giving up on 145.142.151.96 .

Any ideas?

Next problem:

We have two servers both with Internet Mail Service on (only one is a mail
domain host - one hosts mail.mycompany.com). On both IMS the routing tab is
set to 'Do not reroute incoming SMTP mail' but we have a number of secondary
domains that resolve to the host IP box. First I had 'reroute incoming mail'
and the domains listed eg secondcompany.com, thirdcompany.com but this
seemed to prevent us from being able to send mail externally (I know it
doesn't make sense). How should we have this arranged?

Any pointers or advice gratefully received - our companies have ground to a
halt.

Dan Murray