This is really frustrating. I'm only a small customer but it doesn't seem right that they could take away part of the deal if I have multiple years pre-bought prior to the change.
The email I received is slightly different and doesn't include set dates, it just says "after the first year" which could be tomorrow.
I've emailed them asking for clarification.
I pay for Fastmail, but use several of the gandi basic mailboxes for other reasons. I could live with those disappearing. I hope this doesn't also remove the 'forwarded addresses' though.