You may wish to move your blocked senders list from medschl email to Exchange Online. This will not happen automatically and will need to be done manually after your mailbox has been migrated.
How to move your Blocked Senders list
To do this you need to have access to your medschl mailbox in Outlook
Open up Outlook
Click Home > Junk > Junk E-mail Options
3. Open the Blocked Senders tab and click Export to File. Choose a location to save the file, name and save it.
You will now have a .txt file that you can use to create new blocked senders in Exchange Online
Go to Exchange Online https://outlook.office.com/mail/ in a web browser
Click on the gear icon near the top right of the window
Click View all Outlook Settings at the bottom of the Settings pane.
A Settings pane will then appear.
Click on Junk email
Click + Add
Open up your text file of blocked senders
Paste in an email address and hit the enter key on your keyboard
Repeat steps 7-9 until you have added them all
Other Information
For information on managing junk mail and blocked senders generally please see this page - Junk Email Filter