What version of Adagio Contacts/SalesCQ is your client using?

I do not replicate the problem your client is experiencing, when using SalesCQ 8.1C to email a Mail Merge. However admittedly, I have a completely different problem where database fields are not translated at all on email cover sheets, though everything works as expected in the mail merge document attachment. This is why I waited for confirmation to the question of using prospects, in case they are using a much older version of Contacts that doesn't do this.

This is all I can provide without more direction from R&D.