table
	{mso-displayed-decimal-separator:"\.";
	mso-displayed-thousand-separator:"\,";}tr
	{mso-height-source:auto;}col
	{mso-width-source:auto;}td
	{padding-top:1px;
	padding-right:1px;
	padding-left:1px;
	mso-ignore:padding;
	color:black;
	font-size:11.0pt;
	font-weight:400;
	font-style:normal;
	text-decoration:none;
	font-family:Calibri, sans-serif;
	mso-font-charset:0;
	text-align:general;
	vertical-align:bottom;
	border:none;
	white-space:nowrap;
	mso-rotate:0;}.xl19
	{text-align:left;
	vertical-align:middle;
	white-space:normal;}Is legacyExchangeDN required for Exchange on-premises (2016) and should SDS be writing the field out?”  This is mostly “out of the box” config for SDS.
Microsoft premier support says yes.  A lot of other  articles I can find say yes.  Also when I look at another client running a much older version of SDS, I see that legacyExchangeDN is actually written for those contacts.