I have prepared texts on different languages. On hungarian (my language), on serbian, croatian and english. If someone join me from the first three language territory, I am sending him a welcome letter on his language, to others on english. Letters on every language is the same by content. And every letter is composed like that, that it seems to reader that it is written personally to him/her. They are stored in different folders, and I am just copy-paste them.
Otherwise individual welcome letters are more personal, but if you have good ads on the net, and you got many joins in one day, the group mailing is more practical. Look at the top enrollers. Who could send out a few hundred idividual mails a day?
I have prepared texts on different languages. On hungarian (my language), on serbian, croatian and english. If someone join me from the first three language territory, I am sending him a welcome letter on his language, to others on english. Letters on every language is the same by content. And every letter is composed like that, that it seems to reader that it is written personally to him/her. They are stored in different folders, and I am just copy-paste them.