Reference check letters are merged differently than other mail merges, and must be done here. Trying to do this from any other tools will result in the volunteer getting the letter rather than the person providing the reference!
Click on Print reference check letters from the Applicant screening panel.
Select the type of reference letter to be used. The letter here must be of the type Reference checks and have as its Data sourceCertifications and Certification type of Background reference check.
Click Run to merge the letters.
Print the letters, then save them. VSys will prompt you about changing the status of the reference check requests themselves.
Click Mark as printed/mailed so that VSys knows these letters have been mailed and not to send them again.