Start by sending me emails that I can't opt out of without losing access to the infrequent relevant emails about your services that I actually care about.
Increase the frequency of these emails after your company has been bought out.
Have a breach in your systems such that I receive spam to the email address I use for only your company, deny there was any hack on your systems.
Send increasingly urgent emails about an action I need to take to continue using your service. When I open said emails, let me know you just want me to fill out a survey about your most recent sale.
And finally, send me an email with the subject "FINAL NOTICE," and contents letting me know that the deadline to complete said survey is today.
Well, today is also the day I move away from your services and cancel my account.
Good work, you. You've successfully lost me as a customer.