SymptomsThere are a lot of e-mails in mail queues on a back-end server. Mail can not be sent outside of the Exchange organization.
CauseExchange backend server typically has no access to the Internet or may have an IP address which can not be resolved into the hostname. Due to these facts, direct mail delivery from back-end server to the Internet can be a problem.
ResolutionTo route all mail through a dedicated SMTP relay server. Usually it is a SMTP front-end in the same Exchange organization, but it could be some proprietary "black-box" with anti-spam/anti-virus filtering as well. Let it be EXSMTP01 server in our case.
There are two ways of setting up a mail routing:
1. Define the EXSMTP01 server as a smart host on all exchange servers:
a) Open ESM->First Administrative group->Servers->BackEnd01->Protocols->SMTP
b) Open properties of 'Default SMTP server'
c) Press 'Advanced' on the 'Delivery' tab
d) Enter an IP address (in square brackets) or FQDN of the EXSMTP01 server in the 'Smart host' field.
e) Repeat for all exchange servers you want to route through the smart host.
2. Setup an Internet connector for the current routing group:
a) Ensure that all exchange servers you wish to setup routing for are located in the same routing group (check ESM->First Administrative group->Routing groups)
b) Create a new SMTP connector for the routing group (ESM->First Administrative group->Routing groups->Group->Connectors) and specify EXSMTP01 as a local bridgehead server. On the 'Address space' tab define an SMTP address '*' with some cost (good default value is 50).