In Gmail ---
How to: send to a list of people by bcc (blind carbon copy), but in the Salutation, writing
Dear ...
with their first names.
For example, in
Bcc: N1, N2, N3, ..., Nj, ...
The N1 in the 1st name on the list would receive his/her messages as:
Dear N1,
The N1 in the 2nd name on the list would receive his/her messages as:
Dear N2,
The Nj in the jth name would receive his/her messages as:
Dear Nj,