Filter recipients not in directory 1

[ragnarok75]

Currently I am running Exchange 2003 SP2 and I do not have the check under recipient filtering (Filter recipients who are not in the directory) checked. I cannot find a reason NOT to check this box, however my server is running well and I do not need to create extra problems. I am looking for some feedback on why you would and would not check this box.

Thanks.

 

[58sniper]

Because it can lead to directory harvesting. By not allowing the connection, the sending server will know right away that that it's invalid, and can try another.

If you enable that, you should enable tarpitting to help reduce harvesting attacks.

Pat Richard, MCSE MCSA:Messaging CNA
Microsoft Exchange MVP
Want to know how email works? Read for yourself -

http://www.ietf.org/rfc/rfc2821.txt