Manage multiple email addresses.
If you use Gmail, use Mail Plane App. It's the best!
If you use Mac, consider Air Mail. It's beautiful, organized, and easy to read.
If you're old-fashioned or want the tested and reliable, but don't care so much about how nice the UI is, use Outlook express.
Don't just give away your email address...
...until you definitely want to commit. When you sign up for a free trial, they will put you on their marketing mailing list and will send you many marketing emails.
Inboxes.app is a browser extension that generates a random email address for you. Give that to the free trial or random website signup that you don't care about. If you like the service, you can change the email to your real address. If not, you can just forget about it.
It will generate a random email for you like this "oupkrq@inboxes.app" which you can use for some time, then discard and generate a new one.
(featured)
Automatic email tracking and other improvements
https://gmelius.com - Many features! Good UI. Works with Mail Plane App. Integrates with Trello.
Automatic email tracking. Calendar integration. Chat messaging interface for simple replies. Etc...