The president of a Frederick-based mail preparation service and printing company pleaded guilty to fraud resulting in the loss of about $630,000 to his clients.

Fifty-eight-year-old Chester William Bigelow, head of RMS Direct, faces up to 20 years in prison at his sentencing on June 30.

According to court documents, Bigelow, of Woodbine, falsified postage statements saying that the mailings were being sent out when, in fact, they had not been delivered.

Most of the clients were non-profits that relied on the mailings to raise money for their organizations, federal prosecutors in Maryland said.

RMS vice president Stephen Reid, of Frederick, previously pleaded guilty and is scheduled to be sentenced July 12.