Exch 2007 sp2 ru3. Google returns no results for this mapi exception. NDR when sending to an internal user. Full text is: #550 5.2.0 STOREDRV.Deliver: The Microsoft Exchange Information Store service reported an error. The following information should help identify the cause of this error: "MapiExceptionNotFound:16.18969:90000000, 17.27161:000000005C000000000000000000000000000000, 255.23226:00000000, 255.27962:44000000, 255.17082:BFF9FFFF, 0.25697:0E000000, 4.21921:BFF9FFFF, 255.27962:FA000000, 255.1494:02400080, 255.26426:96000000, 4.9206:BFF9FFFF, 4.7974:BFF9FFFF, 255.1750:00000000, 0.26849:00000000, 255.21817:BFF9FFFF". ## http://exchangedeepthoughts.blogspot.com

It looks like an issue with the nickname file in outlook; so i'll repost this in the outlook forum, but it turned out the "." in the email address firstname.lastname@company.com was removed in the NKF, so it was firstnamelastname@company.com ...very weird!http://exchangedeepthoughts.blogspot.com