with V8.7 sendmail, addresses with and without a
host part that resolve to local delivery are handled in the same way.
For example, user and
firstname.lastname@example.org are both looked up with the User
Database (userdb) and processed by the
localaddr rule set 5 (Section 19.6). This processing can result in those
addresses being forwarded to other machines.
stickyhost feature, you can change this
stickyhost, you are telling
sendmail to mark addresses that have a local
host part as “sticky”:
user ← not sticky email@example.com← sticky
Sticky hosts tend to be delivered on the local machine. That is, they
are not looked up with the User Database and are not processed by the
localaddr rule set 5.
One use for this feature is to create a domainwide namespace. In it, all addresses without a host part will be forwarded to a central mail server. Those with a local host part will remain on the local machine and be delivered in the usual local way.
Note that this is opposite the behavior of the former
notsticky feature of V8.6.