Every step below is from an official source
Switch from Gmail to Outlook.com
What to do at Gmail before you leave, what Outlook.com needs when you join, and everything else the switch touches. Your full plan is built in your browser and stays there.
Official sources reviewed . How we review sources
At Gmail, before you leave
Forward new Gmail messages to your new addressBefore
In Gmail settings, open the Forwarding and POP/IMAP tab and click Add a forwarding address. Click the verification link sent to the new address, then select Forward a copy of incoming mail to and save.
Expect only new mail to be forwardedDuring
Gmail forwards all new messages to the other account, except spam.
Download your mail and contacts with Google TakeoutBefore
Go to the Google Takeout page, choose which products to include, then select Create export. Contacts are exported as vCard.
How to download your Google data - Google Account HelpGoogle. ReviewedKnow that a removed Gmail address is retiredAfter
Download your data before removing Gmail. Gmail deletes your emails and settings after 30 days, and no one can use your Gmail address in the future.
Remove Gmail from your Google Account - Computer - Gmail HelpGoogle. Reviewed
At Outlook.com, when you join
Forward your other account's mail to Outlook.comDuring
Outlook.com no longer lets you connect new third-party accounts such as Gmail. To read that mail in Outlook.com, set up forwarding in your other account.
Connected email accounts like Gmail and Yahoo not working in Outlook.comMicrosoft. ReviewedImport contacts from a UTF-8 CSV fileBefore
Microsoft's contact import guide, which applies to Outlook.com, recommends a CSV file with UTF-8 encoding so all text shows correctly.
Import or export contacts in Outlook using a .csv fileMicrosoft. Reviewed
Then: everything else the switch affects
The steps above are what Gmail and Outlook.com say. Your full checklist adds the accounts, codes, payments and devices that depend on your email provider, in a safe order. It's built from your answers, in your browser.