I wanted to express our appreciation for the great service your company has provided us. We have been extremely pleased with your consistent effort (you've always been here like its drawn up by your contract), communication (those email updates you send when wintery weather is incoming are so useful), and delivery of the service that we pay for (you've never charged us anything beyond our agreed upon fees).
I know our tenants had difficult times in the past with snow removal, but your staff has really performed outstandingly to keep them happy. In addition, we are very pleased with your attention to detail and the quality work your staff do for our tenants. Keep up the good work and know that it is very much appreciated by us.