You have a Microsoft $365$ E$5$ subscription.

A user attempts to send an email message to an external recipient and receives the following error message: $$Your message couldn$$t be delivered because you

weren$$t recognized as a valid sender$.$ The most common reason for this is that your email address is suspected of sending spam and it$$s no longer allowed to

send messages outside of your organization. Contact your mail admin for assistance. Remote Server returned $5505\mathrm{.}1\mathrm{.}8$ Access denied, bad outbound sender$.$

You need to ensure that the user send email to external recipients. What should you do$?$

A$.$ compliance management in the Exchange admin center

B$.$ Data loss prevention in the Security & Compliance admin center

C$.$ Threat management in the Security & Compliance admin center

D$.$ action center in the Exchange admin center