Mass Editing Letters

[Earl White]

Hello BiggerPockets Community, I recently launched a direct mail marketing campaign, and am sending out 30+ letters per week. I have had a strong response rate, but it is time-consuming to tailor each letter (personal name, tweaking singular/plural, fixing grammar, etc.) Does anyone know of any software to expedite this process? How do other marketers get out letters quickly? I do not want to use a professional company for these purposes, as I handwrite the envelopes, include business cards, and use bond paper.