The Huddersfield-based business has not specified the length or value of the contract, but said it is a "long-term" deal. HML previously handled print management in-house.
Adare will be responsible for transactional mail, customer communications, mortgage statements, notification letters and rate change information. It will do lasering, enclosing and distribution.
Adare chief executive Robert Whiteside said: "This contract highlights how in the current climate, some companies are recognising that even critical areas that have tended to be kept close in-house can benefit from an outsourced solution.
"It signals a great opportunity for Adare to be working with one of the key players in the mortgage market and we look forward to developing the relationship and extending the service we can offer them over the coming years."
HML business services director Andrew Jones added: "When we weighed up all the options available to us, we felt confident that the whole process could be transferred with no disruption to the level of service we provide. Adare has also provided us with a future proof solution that gives us greater scope to accommodate our own growth plans."
See also:
Adare seals multi-million pound deal with Whitbread
Adare opens new warehouse after outgrowing existing site