I was performing a cleanup of old user accounts on our Exchange 2007 server and deleted two accounts that belonged to s specific distribution group. One set of lawyers uses this distribution group for email communication and scheduling meetings via shared calendars. Since the deletion of these two user accounts, each time an event is scheduled using the distribution group, the person scheduling the event gets two Exchange error messages with the following: IMCEAEX-_O=FIRST+20ORGANIZATION_OU=First+20administrative+20group_cn=Recipients_cn=user@abc.com #550 5.1.1 RESOLVER.ADR.ExRecipNotFound; not found ## Each email message pertains to the two accounts that were deleted. I have checked each user account that is still a member of the distribution group. Neither of the deleted accounts is listed as a forwarding address, neither have send as rights or full access permissions. I checked each existing user's Outlook settings. The deleted users are not listed in email or calendar as having any rights to the inbox or calendar. I have been to each of the existing user's workstation and deleted the Outlook.N2K files. I have deleted the distribution group and recreated it. That didn't work, so I deleted it again and recreated it with a different SMTP email address and alias. Now, if you send an email to the distribution group, you get no error messages. If you schedule a calendar event and use the distribution list as the invitee, you get the error message. Any ideas?

Hello LBT, This seems emails are still send to the users who have been deleted. If you schedule a calendar event without the distribution list, will this issue occur? Make sure there isn't forward or delegate settings. Thanks, EvanEvan Liu TechNet Community Support