I had the same problem, with a few additional kinks, and after initial difficulties I was able to unblock myself. Since there’s no mention of where/how you tried to unblock yourself, I don’t know if you already tried this. I had to unblock myself differently than I have unblocked other people. Hope this helps.
Go to Settings—> Apps—> Mail—> Blocked—> then Find your name and email addresses; in my case they were near the bottom of my very long list of Spam callers (mostly phone numbers, even though this was under the Mail App). Tap Edit at the top right of the window/screen—>tap the “-“ sign in front of the inappropriately blocked accounts, one-by-one (or possibly they can be marked and then unblocked all at once—I did not try that), and —> Unblock.
One of the initial difficulties I encountered was that the “Edit” option did not show up at the top of the window at first; I had to close Settings, and then reopen it. I don’t know why my iPhone 13 is being so quirky. I’m currently using iOS 18.4.1, which I will update once I free up enough space on my phone. 🙄
I went back and checked and the blocked symbol was gone from the emails. My situation was a little different in that respect because I had previously set my Mail Preferences to leave blocked emails in my Inbox instead of Send to Trash.
[I have no idea how my email accounts became blocked. Nowhere in my iPhone Phone Contacts App did it reflect that my email accounts were blocked, but the red circle with a line through it was showing up on emails I sent to myself.]
I know this was a long explanation, but hopefully it helps you, or others.
