I have been asked a question by someone to whom this has happened. Basically, he had some months ago booked two separate round trips to and from the US. Yesterday he received (and read) two emails advising him that the outbound trip had been cancelled and that he could reschedule the flights -or- click a button to receive a voucher for future use - valid for a year and refundable after a year if not used. He didn't take any action because he was waiting to see what they were going to do about the return legs. Sure enough, some time later, he received (and read) another two emails making the same offer for the return legs. Not being quite sure what he wanted to do, he took no action for a couple of hours. When he subsequently went back into the first email and clicked on the "Claim a voucher" button - it led to a page that was no longer available. On the off-chance that one of the other emails might work, he went into the other "Outbound" flight email and realised that the sentence about the voucher had disappeared from that! He checked the other emails and discovered that that particular sentence had now disappeared from the first three emails but not from the last (fourth) one received. I know that using some email software, it is possible as a sender to "Recall" a message. However, I didn't realise (had never even considered the possibility) that it might be possible to "amend" an email after it has been opened and read. Does anybody know anything about this?