I am trying to use bulk mailing/mass mailing to a large number of recipients.
However, the emails must go out in different languages.
In a related question the accepted answer states the following:
For the multi-lingual use case, you might consider creating a template per language as many of our other customers do.
So, how do I specify a different template (each template is in a different language) per recipient when sending out emails in bulk?
You can't specify different template per recipient. But I guess you have a number of recipients per language. You can send separate request for each language group and specify corresponding template.
Also if your template isn't big, you can put some of the language strings in recipient level substitutions. That may not ideal for all cases though.