According to RFC 5545 - Internet Calendaring and Scheduling Core Object Specification (Icalendar)
RRULE:FREQ=YEARLY;INTERVAL=1;BYMONTH=12;BYMONTHDAY=-1
Is a valid value. But aspose-email-26.3-jdk16.jar fails to parse i…...Core Object Specification (iCalendar) RRULE:FREQ=YEARLY;INTERV...