Mail app: Maximum number of blocked contacts reached

There has always been a limit. However, in the past, that was never made explicit, and people became annoyed when email addresses or numbers that they had thought they blocked weren't really blocked. Apple is now making people aware of that. I don't know that Apple has given an exact number, but people report that it's probably 3000.

Blocking is not a useful anti-spam strategy. Spammers don't use real email addresses or phone numbers. They also change things regularly. Blocking is only really useful for blocking real people or businesses, e.g. your ex brother-in-law who still wants to get together even though you keep telling him no, the Red Cross who keeps calling to ask you to donate blood even after you've told them repeatedly you have a medical condition that makes that impossible, or (and I hope this never happens to you) the ex partner who keeps leaving nasty messages.

For email spam, you should either use the spam filtering options provided by your email provider or look into third-party options such as the highly regarded Spam Sieve. For phone calls, use the new built-in screening options in the Phone app.

If there is always been a limit, does that mean that before this pop-up was available to be displayed upon reaching the limit, it was erroneously marking an email address blocked?

I don't know whether or not that was the case, and while I did complain that there are many ways to increase the entries that could be put in that list, the primary source of my frustration is the lack of documentation as to what the limit is, and constant failures when attempting to delete what I think are the oldest entries (which currently isn't possible for me, unless I can remember the recent addresses blocked, perhaps) is just a guess - is the list displayed oldest to newest or newest to oldest, or some other order altogether? And since only one blocked contact is listed as an individual contact entry, and every other is combined as "2586 unknown" entries together, an attempt to delete more than a couple of the unknown list of entries at once results in the spinning beachball, and then eventual crash of the service that System Settings panel uses - and a System Settings search doesn't return anything for "blocked contact" after that crash, or anything similar. Many log entries indicate error messages until a fault and crash whenever I try to delete a few at once, and when I do find a way back to that panel in System Settings, I see nothing was ever deleted.

If those entries are in some sort of sql table, as I suspect, is it accessible to modify directly?

I'm also using other strategies to lower that amount of phishing/spam messages being received, but a lot of them I would think never should have made it past Apple's filtering system that all email have to go through, before my iCloud filters and the Bayesian filter on Mail.app get it. It seems their first filters allow way too may emails through with nonsense addresses that shouldn't pass the DMARC checks and other ways that Apple uses when filtering incoming email its iCloud mail servers, according to Apple's documentation provided and available to business marketing departments about how to not bounce its marketing email to iCloud email addresses.

draklorimed188 wrote:

If there is always been a limit, does that mean that before this pop-up was available to be displayed upon reaching the limit, it was erroneously marking an email address blocked?

No, it means that only the first 3,000 entries were searched for a blocked email.

And in answer to the rest of your post, blocking email addresses that sent spam is totally useless, because spammers don’t reuse email addresses. So you have thousands of emails blocked that will never send to you again. See this tip:

How can I block email spam? - Apple Community

See my user tip: How can I block email spam? - Apple Community