As part of the agreement, two Pitney Bowes engineers have been employed full time to support £5.5m-turnover Staffordshire-based PHD.
The engineers will look after all of PHD's machines, including equipment from non-Pitney Bowes manufacturers.
PHD Mail business development manager Kevin Dunn said: "Multi-vendor service makes total sense to us. We can deal solely with Pitney Bowes whenever issues arise, and we have two engineers on site, six days per week, enabling us to keep productivity levels at the maximum."
Through the service, PHD Mail has a fixed price for all parts and labour, which Dunn said allowed 53-employee PHD to budget and plan ahead with more confidence.
Pitney Bowes' multi-vendor service provides printers and mailing houses with a single point of contact for all of its mailing equipment service requirements.
Gareth Stoten, general manager of Document Messaging Technologies UK & Ireland at Pitney Bowes added: "We are seeing more and more interest in the multi-vendor service approach. Having just one point of contact to turn to for all service queries enables PHD Mail to focus its time on providing customers with quality and value."