As of today’s site update, you can now add alternative email addresses tied to your account. In your profile, go to Preferences → Account → Email and click + Add Alternate Email. You will have to follow a link in two confirmation emails; first to your primary email address, and then to the new alternate email address, to add the alternate address to your account. If you have two-factor authentication (2FA), which we strongly recommend, you will also need to use your second factor to authenticate adding the new alternate email address.
At this time and for the foreseeable future, we do not enable any of the incoming email features at MakerForums, and notifications are sent only to your primary email address, so this feature is of limited value at this time. However, if you want to alternate between primary addresses easily, this feature may be useful to you.