Sorting by a specific field is not applied to whole selection of emails.
If for example a search is performed and 200 pages of results are obtained, they can be sorted by fields - e.g. the "from" field. They will be sorted on that page, but when moving to the next page they will be sorted differently on that page. i.e it does not perform the selection across the whole selection of e-mails
Waiting for a fix in a future release of Archive Manager