Merging leads in Microsoft Dynamics uses the Two Options type - Sync filter = Yes (TRUE) and Sync filter = No (FALSE). When you merge two records, the result varies, depending on which record is True and which is False.

The lead records become true or false based on the workflow rules defined by the admin to determine the winner. The sync filter for the winning record is what ultimately determines if the MS Dynamics record syncs with Marketo.

It’s when one record is true and one is false that it gets tricky.

If the sync filter for the losing record is:	and the sync filter for the winning record is:	This is the result in Marketo
True	True	The winning record continues syncing with Marketo
False	False	The winning record continues to not sync with Marketo
False	True	The winning record will sync with Marketo
True	False	The winning record will not sync with Marketo