By default in our Salesforce org, the 'notify user' checkbox is unchecked when you go to reassign a Contact to another user, but when Contacts are reassigned via Marketo, users are being notified.
Is there anywhere in the sync set up where we can disable these notifications?
I can see that there is an option to uncheck the trigger email notification for Leads being assigned, but would this apply to Contacts as well?
I suggest you open a ticket with SFDC support.
I did find these articles that reference your issue
https://trailhead.salesforce.com/trailblazer-community/feed/0D54V00007T4VQtSAN
@mwongg Agree with @NicoleMarcoe1 this should be a SFDC CRM support ticket or connect with your Salesforce Admin to resolve the settings.