Is it Possible to Seamlessly and Losslessly Transfer a Comcast.net Email Account from one Xfinity Internet Service Account to Another?

I have had Comcast internet service for roughly 25 years.  Aapproximately 15 years ago, a friend of mine ("Friend") was moving from one location, where Friend had had Comcast internet service (and therefore a Comcast email account and a Comcast.net email address) to a location where Comcast service was not available.  Friend understandably did not want to lose either his email messages or his Comcast.net email address.  As an accommodation, I offered to allow Friend to move his Comcast email account to within the scope of my own Comcast Internet Service Account, if that were possible, because I was not using all of the theoretical maximum of email addresses (five, as I recall) that could be housed within the scope of my Comcast Internet Service Account.  We contacted Comcast Customer Service and spoke with a staffer who walked us through the process.  I don;t recall the precise details, but the transition occurred without any hiccups.

Friend now shows up as a Member (and "secondary user) under my Xfinity Internet Service Account.  My Account shows that Friend has two email addresses associated with his Membership under my Xfinity Internet Service Account: the email address that he did not want to lose ("friend@comcast.net"); and another ("friend@yahoo.com").

Comcast has since introduced service into the area where Friend has lived for ~ 15 years.  Friend has taken out his own Xfinity Internet Service Account at that location.  In doing so, Friend set up his own Xfinity Internet Service Account using a different email address than "friend@comcast.net".

What we would now like to do is to *seamlessly* and *losslessly* shift the "friend@comcast.net" email account (that is, both the "friend@comcast.net" email address as well as the contents of the associated mail boxes) from my Xfinity Internet Service Account to Friend's own relatively new Xfinity Internet Service Account.

Is it possible to accomplish that objective?  If it is possible, then how can we accomplish that objective?  What steps should we take, and in what precise sequence?

I know how to remove Friend as a Member and secondary user from my Xfinity Internet Service Account, but that will likely result in the loss of the contents of Friend's mail boxes, and the "friend@comcast.net" email address might not immediately become available to Friend so that he can assign that email address to his own Xfinity Internet Service Account.

Thanks in advance for any guidance.