Microsoft previously worked with a number of small agencies but has consolidated the account between Wunderman and McCann-Erickson Worldwide's MRM Partners.
John Kahan, general manager of Microsoft's corporate CRM Group, said: "We decided to align with two of the best agencies worldwide with world-class skills."
According to sources, the move was made to exclude the possibility of conflicts. Wunderman previously shared duties on IBM with sister shop OgilvyOne and could not have taken on Microsoft without giving up IBM.
The IBM business was previously split along business divisions: OgilvyOne handled solutions and server groups and Wunderman worked on the personal computer, software and global service units.
Oglivy & Mather New York has handled IBM's global advertising since the early 1990s and according to sources IBM is comfortable with the relationship, which has prompted the direct marketing move.
The value of the IBM account has not been determined.
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