Any suggestions on how to do this would be welcome. I suggested to support that "others" had successfully had the limit removed, and they were dubious.

I just spent an hour with Support and they confirmed that the email forwarding/mapping feature should still be functional, however edits to the rule (additions, deletions, changes) are disabled, and new rules are not allowed. No ETA on a resolution. ...

We are there with the "unique mapping" crowd. I have just shy of 1,000 email mapping items that correspond to the same number of logins across various platforms. I don't like the idea of paying for that service beyond this new spontaneous limit, but ...