The msp feature can take an optional argument. That argument determines whether the mail collected by the MSP invocation of sendmail should be delivered to the local machine or to another machine:

FEATURE(`msp')               deliver to localhost
FEATURE(`msp', `otherhost')  deliver to otherhost

If this optional argument is given to the msp feature, that argument is assigned to the ${MTAHost} macro. If this optional argument is absent, the value assigned to ${MTAHost} is [localhost]. The square brackets around localhost suppress the lookup of MX records.

All messages will be forwarded to the ${MTAHost}. If you wish to suppress MX lookups for the ${MTAHost} host, surround the hostname with square brackets when you declare it with the msp feature:

FEATURE(`msp', `[otherhost]')

See Section 2.6.2 for a description of how to install an MSP server, and FEATURE(msp) for a description of the msp feature.

You should never use this ${MTAHost} macro directly because it might change in a future release of sendmail. Use the msp feature macro instead.