Automate and customize email for previous months contacts?

Hello
Long time reader on here but very new to email marketing.This is for a portion of my job that is not strictly email marketing, but just trying to keep in touch with leads and I felt this forum would be the best place because the use I am looking for is probably email marketing! Looking for advice for a service for something particular:

Automating emails to previous months customers.

Have about 50-80 new people each month in my excel list that I work on. Spend a lot of time and effort catering to the current month's people and hard for me to get around to previous month to check in. I want something that will occasionally automatically ping my previous month's leads for me.

Looking for a service where I can input clients information and date of initial contact and have it automatically do something like these:

A) Hello [customer], You contacted us [X] number of months ago about [A or B] . Can I still be of assistance to you?

etc etc.

I think you get the idea.
Anything that can automate this from my works email address , so that response go to my work email?

I guess I dont have to cater to a full year of leads at once, but I would like it to cater to 2-4 months worth of people. So that as they age past 4 months, they are not included in this sort of outreach