Question changes to postifix main.cf in Plesk 17.8

[TobiasP]

Hi,
It seems that the upgrade to Plesk 17.8 added two new lines to my postfix main.cf:

recipient_canonical_classes and recipient_canonical_maps

I only noticed because they were not added on a new line but instead appended to an existing configuration line I added (and broke the config in the process)

Could someone explain why these two options were added in 17.8?

Thanks,
Tobias