You can allow the server IP address in the Connection Filter. This would achieve the objective of ensuring all email from Fabrikam.com is delivered. However, it would also allow any other company that uses the thirdparty email server to bypass the spam filter.
The fact that the question specifies that Fabrikam uses a "third-party messaging solution" suggests that the answer to this question should be No although technically it would work.
Reference:
https://docs.microsoft.com/en-us/microsoft-365/security/office-365-security/create-safe-sender-lists-in-office-
365?view=o365-worldwide