In some cases if this creates problem after e-mail migration. In NK2 file old email address is cached.
So while sending a new mail it fetches from cache and mail bounces.
In such case search for *.NK* files and delete them.
usually found in c:\documents and settings\profilename\application data\microsoft\outlook.
After restarting outlook it will create another .NK2 file and fresh caching starts.
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This also happens when we re-create a user profile or move to different PC and have fresh windows profile. In that case if we create a new email profile (e.g. new ) Then after opening outlook once, close it and then go to c:\documents and settings\profilename\application data\microsoft\outlook folder. You will see 3 files as below.
new.srs, new.xml & new.NK2
Here copy the 3 old files (old.xml, old.srs & old.NK2). Rename the old with new.
Then start outlook, it will start fetching cached entries which were stored earlier.
