Copy the whole subject from the previous mail. In the new mail write “Cancelled: 1465800000XXXXX - “ in the subject and then paste the whole subject that was copied. Example - Cancelled: 1465800000XXXXX - XXX Hotel (19 Dec, 2019 - 26 Dec, 2019)
From the previous mail copy the email address that is mentioned in “To” and paste it at the same place in the new mail.
Tap on the down arrow on the “Send” button and click on the “Send right now” option.