An empty mailTo is valid - https://en.wikipedia.org/wiki/MailTo.
We have a calendar invite with an attendee that has an empty mailTo - e.g. -
ATTENDEE;CN=John Doe;CUTYPE=INDIVIDUAL;PARTSTAT=ACCEPTED:MailTo:/O=ABC/OU=DE…...Aspose Email fails to parse eml with calendar invite with an...containing an empty mailto Aspose.Email Product Family gs01 October...