A. Not necessarily—and even then, that doesn’t have to come at the cost of abandoning your old address overnight.
The job is easiest at Microsoft’s Outlook.com, where you can create a new “alias” for your account that has a new e-mail address but keeps all your messages and contacts in the same place. Sign into your Outlook.com webmail, click the gear icon at the top right, choose “Connected Accounts,” and then scroll down to “Manage or choose a primary alias.”
On that page, create a new Outlook.com address, then click the “Make primary” link to have that become your ongoing identity on Microsoft’s service.
Yahoo Mail offers its own alias feature. To create a new address linked to your existing account, log into Yahoo’s webmail page, click the gear icon at the top right, click “Settings,” click “Accounts,” click your Yahoo account and scroll down to “Extra email address.” You can then make that new address your default under the “Writing email” settings category.
(Disclosure: I write for Yahoo’s Yahoo Finance news site, but I have zero input into the workings of the company’s email service.)
Things are much more of a mess at Google’s Gmail if you don’t have a new e-mail address at another mail service, which you can set as your alias there. Otherwise, you have to create a new Google account, then set your old Gmail account to forward messages to the new one.
To configure Gmail to do that, log into Gmail on the web, click the gear icon at the top right, choose “Settings,” and click the “Forwarding and POP/IMAP” tab. You can then instruct Google to send change-of-address messages to people who email you at the old address. Click back to the main settings page, then scroll down to “Vacation responder.”
What about your old emails? The simplest way to bring them over is to set Gmail to download them from the old account to the new one. In the old one, click to the “Forwarding and POP/IMAP” Settings tab, then enable “POP downloading.” Then go to the new account, click the same Settings tab, and configure it to download everything from the old account. (“POP” stands for “Post Office Protocol,” a basic standard for fetching messages for offline reading. Because it predates mail syncing among multiple devices, it won’t preserve details like any labels you added to your old messages.)
Moving over contacts requires exporting them from the old account and importing them in the new one, while you can move calendars by transferring ownership of them to the new account.
If all that work leaves you questioning the wisdom of being married to Google, I can’t blame you.