Dear Krisada-san,
Do you mean below? ;
How many customers can we send 1 email to?
( i.e. How many customers can we include in the destination of 1 email?)
If you mean above by your question, we'll answer that it is depends on the size of email you want to send.
Please let me know the size of email you want to send.
If we have misread your question, please let us know more detail about your question.