Our Exchange system has had to co-exist with an Exim mail server for many years now with this server hosting our primary mail domain used for all external communications (the Exim server is not maintained by our department). This has always caused some confusion when differentiating between internal and external mail, I'll try to illustrate this below using example domain names: All of our external accounts use the mail domain name @externalmail.co.uk Mail is sent and received by Exim server running outwith our Active Directory domain Outlook clients set up to be able to send and receive using this as an internet mail account Our AD setup is @ourdomain.com Internal mail can be sent using (for example) internaluser1@ourdomain.com but mixing internal and external mail accounts causes messages not to be delivered. Our Outlook clients have both the Exchange and internet email accounts set up to allow use of both My plan is to get the Exim server configured to forward on all of our @externalmail.co.uk accounts to our Exchange server and to allow emails to be sent out via the Exim mail server or resolved internally depending on the mail domain extension. There is a slight issue in that some of the @externalmail.co.uk accounts are linked to users in our AD domain and others belong to the department who run the Exim mail server. So if I wanted to send an email to externaluser1@externalmail.co.uk I don't want it to try to be sent locally but it should go out via the Exim mail server. Alternatively, internaluser1@externalmail.co.uk mail should be routed into our Exchange server but should also resolve to a local user account as well. To try to set this up I've configured a smarthost to allow mail to be sent via the Exim server and this seems to be working ok. I also got a couple of test accounts set (test1 and test2) that are currently configured to route directly to our Exchange server via the Exim server. This routing also seems to work fine and using these accounts I can set upa Outlook configuration that only has an Exchange email account and which also can email to internal and external email addresses. For example.... if I try to email internaluser1@externalmail.co.ukusing either of these test accounts this works ok. However, emailing externaluser1@externalmail.co.ukresults in a delivery failure. I hope the above description isn't too confusing but I think I does cover the setup we have here. Would anyone be able to give me some advice as to how I should be setting things up? I know the simplest solution would be obtain a unique mail domain name and use MX records to route the mail directly to us and then set up our own SMTP service to mail out with. However, senior management has stated categorically that we need to preserve the same @externalmail.co.uk type extension so we have to somehow work around this. Should we be looking at sending all our mail out via our Exchange 2007 server but setting it up so that it looks like the mail originates from @externalmail.co.uk - is that a possibility and if so should we ditch the smarthost and look at another way? Many thanks in advance.

Hi, If I understand your setup correctly the "@externalmail.co.uk" needs to be configured as an internal relay domain (instead of an authoritative domain) in exchange 2007. This will make sure that all mails for internal non exchange 2007mailboxes will be delivered to the other mailhost. Leif

Thanks, Leif We have the added complexity of having a mixed Exchange 2003 / 2007 environment as well but I didn't want to make my above description even more convoluted! Anyway, that seemed to do the trick once I updated the Exchange 2003 recipient policy that we have as well so that "@externalmail.co.uk" was unchecked on the 'This mail domain is responsible for all mail delivery to this address' option. I couldn't switch from authoritative to internal relay until this was done (which makes senseI suppose!). Thanks for your help Robbie