Configuring Mailflow

Here is the issue. If you use DNS to route your mail then you will have a problem with sending emails between organizations. In order to make this work you must create a send connector that routes the traffic to and from the organizations. Another way to solve this problem is to use a smart host:

New-SendConnector -Name "Internet" -Usage "Custom" -AddressSpaces "SMTP:*;1" -IsScopedConnector $false -SmartHosts x.x.x.x,x.x.x.x -DNSRoutingEnabled $false -SmartHostAuthMechanism "None" -UseExternalDNSServersEnabled $false -SourceTransportServers "Exchange Server"

Receive Connector:

Now we must tick the Anonymous box on the default receive connector so internet users can send to the Exchange Server:

Set-ReceiveConnector -PermissionGroups 'AnonymousUsers, ExchangeUsers, ExchangeServers, ExchangeLegacyServers' -Identity 'LABDCEX\Default LABDCEX'

Setting External FQDN

Our next step will be to make sure we put the external FQDN on all of the virtual directories.

OWA:

Set-OwaVirtualDirectory -Identity "owa (default web site)" -ExternalUrl https://mail.exchange.lab/owa

ECP:

Set-EcpVirtualDirectory -Identity "ecp (default web site)"  -ExternalUrl https://mail.exchange.lab/ecp

Active Sync:

Set-ActiveSyncVirtualDirectory -identity "microsoft-server-activesync (default web site)" -ExternalUrl https://mail.exchange.lab/Microsoft-Server-Activesync

OAB:

Set-OabVirtualDirectory -identity "oab (default web site)" -ExternalUrl https://mail.exchange.lab/oab

AutoDiscover:

Now autodiscover is a little different with a multi-tenant deployment. The issue is you will have multiple domain names. Now we all know that autodiscover uses SSL certificates and we don’t want to buy a SSL certificate for every domain name we host.

Luckily there are two alternatives. One is you can use SRV records, and the other is autodiscover redirect. SRV records do have a problem though. Some devices may not check SRV records when trying to discover the email settings. I wasn’t able to get this to work on my iPhone, and Outlook 2007 requires a patch in order to make this work.

Your best bet is just to go with autodiscover redirect.