If you are referring to updating the body of an email that has already been delivered to a recipients inbox then no this would not be possible due to restrictions put in place to protect recipients inboxes. Emails are sent using SMTP protocol and are unable to be recalled once delivered. If you were able to recall it would expose a security risk as external parties would be able to pull emails out of a recipients inbox and modify. As result it's impossible for HubSpot or any ESP to modify a sent email structure.
If you are referring to updating the body of an email that has already been delivered to a recipients inbox then no this would not be possible due to restrictions put in place to protect recipients inboxes. Emails are sent using SMTP protocol and are unable to be recalled once delivered. If you were able to recall it would expose a security risk as external parties would be able to pull emails out of a recipients inbox and modify. As result it's impossible for HubSpot or any ESP to modify a sent email structure.