I recently (Wednesday) signed up for Plex and plex pass. The next day I had over 3200 spam messages to the e-mail address I used, the same for today. I don’t know what is happening with your. I’ve had this account for 20+ years and have never had an issue with it until I signed up for Plex.
i don’t know about anyone else but i never got an increase in spam when i signed up. But i do run a couple email servers and know that spam has been getting crazy lately unrelated to plex.tv, i’d suggest contacting your administrator and let them know, especially if its a work email account. they can easily take a look at a sampling of the spam and block them.
This is a Yahoo account that I’ve had for about 25 years and never had a problem before. I have been blocking the spam as it hits my inbox, most has gone directly to my spam folder thankfully.