If ever you get cross pollinated contact cards then you have just been a victim of Lync Contact Merge. A good explanation of this is found here. Its a handy feature but not always desirable…

I landed up with this by normalizing the numbers in AD to a common DDI for all non DDI Telephone numbers in AD – not a good idea 😦

My scenario was that a number of users in AD had 4 digit extension numbers set for their Telephone Attribute. Now we all know that this is not going to make the ABS happy as the import requires a + to deem the format acceptable.

*Simply adding a + in front of the ext number wont work as the Lync Normalization rules DON’T apply to numbers that have been imported from AD.

What we want to achieve is a unique number in AD and thus in the ABS to avoid Contact Merge. We also want all the non DDI users in AD (who live on a legacy PBX) to dial a common DDI which presents a prompt to select the extension (a function on the Legacy PBX).

The Solution…
Normalise the AD Telephone Number field to the Common DDI BUT add the actual Extension number on the end of the normalized number. This will ensure that the Attribute stays unique and it will also be a valid number to dial. When the normalized number is passed to Lync for calling it ignored the normalization rules as stated above at *. The number is sent “as is” to the mediation server and thus passed on to the Provider, who simply ignore the extra digits on the end of the valid E.164 number.

Ta Da