The list of exceptions is a list of mailboxes, mail from which will not automatically be taken into account when merging and grouping into a chain. By default, letters that come from the same box, with the same theme, will be glued together into a common thread.
If you want to see each letter separately, add the necessary boxes to this list. An example of such a box that will lead to incorrect linking of the chains is the manager's box, which is not connected to amoCRM, but is set by managers in a copy of their correspondence.
To exclude the grouping of letters, go to the "Mail" section - the ellipsis in the upper right corner. Then, in the Exceptions section, add the necessary mail, all mail from the addresses on this list will not be automatically counted when merged and grouped into a chain.
And in order that all letters are not attached to one contact, just delete this Contact from the system (delete the very essence to which the letters are attached).
Disconnected grouping of letters, nothing has changed
Previously, the grouped letters already, unfortunately, will not become unstuck. You can also in the "Mail" section, click on "More" in the upper right corner - select the desired box, remove the checkbox "Group letters into chains". General grouping disables further gluing into groups of all incoming letters, but, unfortunately, it does not have the ability to paste those that have been glued together earlier