Well, If at all you are a new sponsor, greet them with a default answer from SFI.
otherwise greet them in your words like, you are their sponsor, if you have any questions let me know by Team mail or SFIM chat.
SFIM's Chat is the best one to communicate, provided they could notice SFIM as chatting media. Else Team mails are good for greeting.
More over we have Stream Posts are also there to greet.
