We're running just Exchange 2010, having upgraded from 5.5 to 2003 to 2010 over the years. I've recently gone through and removed all the old, unneeded x400 addresses from our mail-enabled objects, and i noticed that a few objects, seemingly at random, have x500 addresses as well. Are these needed or can they be removed? I've seen conflicting info ranging from "they aren't needed" to "best not to get rid of them". Thanks, Paul

X500 addresses generally represent a previous legacyExchangeDN value that the mailbox had. If you remove it, cached names, message replies and meeting updates may fail when users send from Outlook to that mailbox. I would leave them since they were originally added to that account for handle those scenarios.

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