2.2.2 [RFC5545] Section 3.1.2 Multiple Values

V0010:

The specification states that multi-valued properties are generally encoded by creating a content line for each value, including the property name. It also describes an alternative encoding, a single content line with the multiple values separated by a COMMA character.

Microsoft Exchange Server 2007, Microsoft Exchange Server 2010, Microsoft Exchange Server 2013, Microsoft Exchange Server 2016, Microsoft Exchange Server 2019

On export, Microsoft Exchange Server uses the single content line encoding method. On import, Microsoft Exchange can parse either method, or a combination of both.