Your email address actually has infinite addresses.
A few years email gained a new feature in adding a + symbol to your address for example:
My public email is hello@greenwood-online.com but if i wanted to use that to sign up to a newsletter i could enter hello+[newsletter name]@greenwood-online.com e.g. hello+hiking@greenwood-online.com
Now when you create a rule you have it based on custom data you specified not someone else, they can change anything they want, their sending domain or a new email address but if they’re still sending to your address with your +[data] included then your inbox rule will also run because you set the rule on YOUR customisation.
Maybe you want to sign up to a newsletter but you’re worried about your data being sold on, again using +[data] will be the address that is sold, so when you start receiving spam, you’ll see exactly who it was that sold you information and have a custom email you can block completely.
This is not just in M365 but any email platform (it’s on by default, can may have been disabled by an admin).
Maybe you have another tool like a ticketing system, using the + can help get emails really easily categorised depending on what you’re receiving an email about.
So stop letting others complicate your inbox, take back control and get your tech doing the heavy lifting to make things tidier for you automatically.
See it in action below: