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!
From the Screening panel under Reference check, click on Generate reference check letters.
Select the letter template to be used. The letter here must be of the type Reference check and have as its Data sourceCertifications and Certification type of Background reference check.
Click Merge to run the letters.
Print the letters and mailing labels if needed, then save them. Once the letters have been saved, VSys will automatically mark the associated reference check requests as "Letter sent".
Click Mark as printed/mailed so that VSys knows these letters have been mailed and not to send them again.
You don't have to send reference check letters every time you enter a reference check request: you can enter many requests over a period of days if you want, then send the letters out in bulk here.