Handling syncs with shared email addresses - strategies?
I'm looking for some strategies to solve a conundrum we have. Many contacts in SFDC share email addresses (for example, generic email addresses used by a department), particularly for customer support contacts. I cannot change this, so please don't recommend this as the proposed strategy! The issue is that if one of these contacts takes part in a marketing activity in Marketo and updates some data to be synced back to SFDC, the activity can be attached to the wrong record in Marketo (e.g. via a list load picking up a different contact with that email address). Then when it syncs back to SFDC, it overwrites data on the wrong contact.
To stop this happening, the SFDC admin has put in a validation rule that stops Marketo updating the contact's name or email address. However, if this validation rule fires once for a sync batch, the whole batch fails to sync.
This is causing data to diverge between the two systems and is interrupting the pipeline by not allowing updates to the contacts, so that Sales can't follow up on MQLs as they don't know they have happened. It is a bit more complicated than that, but that is the gist of what is happening. We can also lose field data if any of the affected contacts sync back from SFDC.
I have suggested blocking the visibility of these contacts from Marketo using a sharing rule in SFDC and then creating purposeful duplicates if the contacts then participate in marketing activities. However, this is not ideal and we'd have to train the sales users (and support users) to be sure that they are using the correct version of the contact in SFDC for opportunities / support cases. Plus, we'd lose the history of marketing activities on the contacts that become invisible.
How have other organisations solved this? I'm sure we are not alone in having this issue. I have seen other people having issues with shared email addresses, but not specifically with the sync. I'd appreciate the insights of anyone who has a strategy to tackle this.