Can't amend or delete email blacklist entries if the username contains a hyphen or equals sign

Can't amend or delete email blacklist entries if the username contains a hyphen or equals sign

In my users' Zoho Mail settings, under the anti-spam option, Zoho has automatically added blacklist (and whitelist) email entries, presumably based on emails being flagged manually as "spam" or "not spam". I'd like to rationalise some of these by adding a black- or white-listed domain instead of having lots of separate email ids. That works fine with most of the entries, and I can amend or delete them. But I have a few entries where the email user includes hyphens and equals signs, for example "mailequity-us=<mydomain.com>@patmagee.org", and if I try to edit or delete any of these it fails with a red-boxed "Sorry, we are unable to process your request" error message, and they stay there unchanged. It's not causing a major problem at the moment, but I would like to be able to tidy them up. I'm guessing there's some sort of SQL or parsing bug (a bit like an SQL injection exploit!) in Zoho Mail that's causing these updates and deletes to fail.