Please explain "Additional Actions" choice on mail-adressee button

[Carolus]

If I left-click the small button next to the mail-receiver's name in the
header of an e-mail, a submenu pops up which , among other choices, shows the
choice "Additional Actions" resulting in "No Additional Actions" found.

Could you please explain this functionality and how it is enabled.

Outlook Help has no info on this feature.

Thanks
Carolus