I guess I use about 10, some are for testing only as I work in project that involves email. For real use I have two:
I have a gmail address I use for all general private mails and one I use for my company mail in the company domain.
I have an email running on my domain, where I use one address mostly, though I can create additional addresses for testing. This is running on a G-Suite account that I created when it still was free.
I have accounts on hotmail, aol, yahoo, gmx, mail-com and few other email services sometimes used to test if a mail works either way (e.g. from aol to the mail service we do).
I also have a subdomain for throw-away email addresses that I can create and remove as necessary which forward to the primary gmail address (if you could these as addresses, its probably another 10–15)
I also have a email addresses on some smaller email services like openmailbox which I created just to test the service (which is offline now, good thing i never used that for anything real).