Hi Simona,
First of all, Marketing email is not the same thing as Activity email as they are two different entities and only the email can be tracked.
However, if you can find the Marketing emails sent to the contacts in your outlook, they are still able to be tracked. This is the equivalent of copying a Marketing Email into an Activity Email. You can set an email address which has been configured in Dynamics as the Reply-to Address in the Marketing email, so that if the contacts reply to the email, the replies can be tracked. Of course this is not a very ideal solution but there is no better solution at the moment.
In addition, although Marketing Emails are not automatically tracked, interactions about them are still associated with contacts and you can view the insights tab for each contact to get the Marketing Emails associated with that contact.

If this helped you, I'd appreciate it if you'd mark this as a Verified Answer, which may in turn help others as well.
Best Regards,
Nya