Log into webmail by going to https://outlook.office.com and logging in using your Smithbucklin email and password. Make sure you have your phone handy because you may have to approve a Microsoft Authenticator request.
Next, click on your profile picture in the top right corner. and click on "Open another mailbox"
A window will appear. Type in the address of the email inbox you want to access, select it from the dropdown menu, and click open.
You may be presented with a login page. If this happens, enter in SMITHBUCKLIN\username (replace the section in bold with your Smithbucklin username) and then your regular Smithbucklin password.
https://activesync.mail.smithbucklin.com/owa/example@example.com
https://outlook.office.com/mail/example@example.com