How do I change my email address on all my accounts?
There's no single switch: each company keeps its own copy of your address, so you change it in each account's settings. Start with the accounts that could lock you out (your Apple, Google or Microsoft account, your password manager, your bank and your phone plan), then work through the rest. Searching the old inbox for welcome and verification emails, or your password manager for the old address, shows you which accounts are left.
Should I delete my old email account?
Not straight away. Forward its mail to your new address and watch what still arrives for a few months: each email is an account you haven't moved yet. Close it only when nothing new comes in. Google says nobody can use a deleted Gmail address again, but not every provider promises that, and whoever got the address would receive the password resets for any account still tied to it.
What happens to an email address I stop using?
Free providers close accounts nobody signs in to. Google may delete a Google account that has been unused for two years, and Microsoft closes an account with no sign-in for two years. After that, password resets for any account still tied to the address go nowhere. To keep an old address as a quiet backup, sign in to it now and then.
Can I forward Yahoo Mail for free?
No. Yahoo's automatic forwarding needs a Yahoo Mail Plus plan. On a free account, check the old inbox every week or two instead, or copy the old mail into Gmail with Gmail's one-time import (Settings, See all settings, Accounts and import, Import mail and contacts).
How do I find every account linked to my old email?
Search the old inbox for words like "welcome", "verify your email", "confirm your account" and "receipt", and search your password manager for the old address. Quitlist can do it for you: connect a Gmail or Outlook mailbox and it lists the accounts it finds in sign-up emails, receipts and password resets. The last 12 months are free.