This can be done using the Office 365 portal.
Microsoft describes it under Inbox Rules in Outlook. Reproduced for convenience.
To manage rules:
In a web browser, sign in to Outlook Web App using the URL provided by the person who manages email for your organization. Enter your user name and password, and then click Sign in.
At the top of the page, choose Outlook (or Mail). Or, choose the app launcher [the grid icon] > Mail.
At the top of the page, select Settings [the gear icon] > Options.
In Options, select Organize email > Inbox rules. Or, in Options, under MAIL > Automatic processing, select Inbox rules.
And then:
If you have a rule that you no longer want, you can select it and then click delete [trash can icon] to remove it. If you just want to turn the rule off for a while, remove the check mark next to the rule.