It is not possible to send multiple E-Mails to each participant in the list.
If I use a comma as seperator when I add the e-mails to the participant, the comma is cut out automatically.

if I use a semicolon as separator, the mail adresses are accepted.
for example
testaddress1@gmx.de;testaddress2@gmx.de

But when sending the invitations the mails are not send because of an error.

at the top there is the message:
Invalid address: Invalid address: testaddress2@gmx.de>