In order to make email links open in Gmail instead of Outlook, you will need to do the following.
When you open Gmail in Chrome, a protocol handler icon appears in the omnibox/webaddress line next to the star bookmarks icon.
Click it to show the following options:
- If you'd like to allow Gmail to open all email links, select the Use Gmail radio button. When you click a hyperlinked email address on a page, Gmail's compose window will open.
- Select No to keep how your computer opens email links the same way as before (ex: Outlook).
- Choose Ignore to prevent the request from appearing again when you visit Gmail.
You will want to select the first option. Then select Done.
Now your email links should open in GMail instead of Outlook.
Learn more at: https://support.google.com/mail/answer/1069522?hl=en