Have I been hacked?

I build via WordPress under my Control Panel. https://www.batgrotto.com is my site. I am not sure how you’d check what software, yet it is www.ads-software.com

I am trying to understand how I received an email for a man to check Admin messages when I changed my Admin email. I received the normal Verification email from WP AND an email for Admin to check unchecked messages.

Here’s there’s the email, I have a pic of it, just not sure if I can post it;
Administration Email <his MSN email address>
Wed 1/27/2021 12:20 PM
Checking Mailbox
Your mailbox account failed to sync and returned (6) incoming emails.
Synchronization was unsuccessful because your mailbox could not be validated.
Check Mail To retrieve.
Note: the message will last until 1/28/2021.

I can hit check Mail to get this link; https://www.notion.so/Microsoft-Access-Page-99538f761ac44d8e805be69fa1a7b771

It actually looks like he can’t get in to check messages, from what that says, yet if he got in Admin some backend way before, he will do it again. He is also not under any Users in WP Dashboard. I would have never known if I hadn’t changed Admin email.

I have his full name and have emailed the company about this that the link goes to and nailed them on Twitter, as well as emailing him to let him know I am turning him in to anyone I can for hacking. Even though he never touched the site, I think he is phishing my info. I will be grateful for any help understanding how this can happen.

The page I need help with: [log in to see the link]