I use Lead Id and Account Id (for converted leads) as the main subscriber key, but there are some cases where they might use Contact ID as the key.
These Id values are different in Sales Cloud for a given user – but would the system recognize that it's the same person if they use both Account and Contact ID? Or would there be separate records/people in All Subscribers?
And when a Lead is converted to an Account/Contact – does the system create a separate record for them because the ID values are different?
Best Answer
If you want to utilise the standard functionality for Marketing Cloud connect (e.g. tracking data integration), you should only use Contact or Lead ID as subscriber key - not Account ID. A single Account ID might also cover more than one contact.
There is currently no ID that links these different IDs together, if they belong to the same individual. Also in cases where a lead gets converted to a contact. The newly created contact ID will not hold any of the engagement data, previously collected for the lead ID. MC will see these as two separate individuals.
There is only a single case, where this data gets migrated, and it is when converting a lead in a Journey Builder activity. However this is very rarely used, as most conversion logic usually sits in Sales Cloud.