Interested to know how others who have similar setup have approached this situation –
We are a project marketing agency and in our EDM footer we include two opt out/unsubscribe links. 1. The default unsubscribe link = they will no longer receive any communications from our company ever again and 2. The project unsubscribe link = they will no longer receive communications for that particular project/ department ever again.
We have almost 60 project unsubscribe programs where if a contact clicks on the project unsubscribe link the contact is then added as a member to a SFDC CRM campaign.
The problem is that our SFDC CRM has multiple records with same email address. This is due to the fact our SFDC CRM was designed and built years ago based on idea that our 5 divisions would always operate in isolation and have no database overlap and hence the SFDC record type ID for each division's contacts is different. However our divisions do have database overlap with many of contacts in SFDC CRM having enquired/an opportunity/ purchase under multiple divisions and hence there is multiple records with same email address.
If a contact unsubscribes from “default unsubscribe” Marketo’s durable unsubscribe functionality will mark all records with that email address as unsubscribed and they will no longer receive any communications from our company ever again.
Where we have an issue is when contact has multiple records and one of the contact records unsubscribes from project unsubscribe for “project ABC” this only adds that contact record who clicked on unsubscribe link as a member of SFDC CRM campaign. The other records that have same email address are not unsubscribed and could potentially receive communications on “project ABC” in the future.
You should use fields and Static Lists instead. I wrote about this on my blog a few times: Subscription Management Center - Marketing Rockstar Guides