Sending a single mail to multiple recipients (multiple recipients in 'To' field) using FM 'so_document_send_api1'

I am able to send mails to individuals (no. of mails triggered are same as the no. of recipients). But when I tried to concatenate the individual email ids seperated by semicolon or space or comma, then mail is not sent successfully and it shows error in SOST 'Invalid recipient address'.

How to send a single mail to multiple recipients (multiple recipients in 'To' field) using FM 'so_document_send_api1'?