Lots of pieces to this here.

Let's start with Duplicates.

Duplicates in Pardot are most often generated from Salesforce.

Common example: if you have two Contacts in Salesforce with the same email address, or a Contact and a Lead with the same email address.

The key here is that EACH of those Salesforce records have different CRM IDs.

When Pardot sees an email address with AND it has a different CRM ID, it will follow what Salesforce does and also create the duplicate.

If you look at each of the Pardot records you can see this - scroll down to the bottom of the left-hand column in the Pardot prospect record. You should see if this Pardot record is syncing to a Lead or a Contact, and what their CRM ID is.

The ONLY way to generate a Pardot-only duplicate? is by hand-typing in a new prospect. And I don't know anyone who does that on a large scale. So while yes, it could have happened, it's unlikely.

You can't get duplicates from form completions. Nor can you get them from importing a CSV file of just email addresses.

Because whenever Pardot gets an email address on its own (whether by file upload or by form fill) Pardot first looks to see if that email address already exists. If it does, it syncs with the existing Prospect record. No duplicates can be generated by Pardot in this way.

Now - if you go do an Import into Pardot, and your CSV file ONLY contains email addresses then Pardot does this de-dupe automatically.

If you do an Import and your CSV file contains a column for Email AND it contains a column for CRM ID, then yes Pardot assumes you're matching Salesforce CRM IDs and it will match up to those CRM IDs. (Important to realize that the duplicate is STILL coming from Salesforce in this scenario.)

So what to do? Well, if you're doing a good job of de-duping in Salesforce then you don't have a duplicate problem.

Because in Salesforce if you are MERGING those records together, then Pardot follows what you did and also merges them.

So in order to reduce duplicates in Pardot? Do it from Salesforce.

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Regarding the message you see "Apply Do Not Email to all records with this email"

This is almost exactly the opposite of what you think it means.

It DOES NOT mean that someone has become unmailable on one version.

If they were unmailable you would see a different message: "Remove Do Not Email from all Records with this Email"

So - leave that link alone. Clicking it would make all versions of them unmailable right now.

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Regarding telling the difference between Hard Bounce and Unsubscribed.

People can become unmailable in several ways:

1) by clicking the Unsubscribe link in a Pardot email.

2) by visiting the Email Preferences Page and clicking to globally opt out.

3) by someone from your company clicking the Salesforce field for 'Email Opt Out' on the Lead or Contact record.

4) because the email address hard bounced (or had 5 soft bounces which = hard bounce)

How do you tell the difference?

Well if it hard bounced you'll see the hard bounce message on the Prospect record (the version of them that bounced).

It's at the bottom of the left-hand column again, and basically tells you what message Pardot got back from the email server. It'll say something like a number error (5.4. or something) and also a text like 'email does not exist on this server' or 'block bounce' or any number of other error messages.

You can also tell tell based on field values. There are TWO fields involved here.

1) Do Not Email (this is a Pardot-only field)

2) Opt Out (this is synced to Salesforce's 'Email Opt Out' field)

If both fields are checked then they unsubscribed.

If only Do Not Email is checked then they hard bounced.

You can create yourself some dynamic lists to sort them out, and see your numbers at a glance. See my blog post about making those lists here:

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Edit:

Specifically to the question of duplicates - when one version of them is unmailable, Pardot makes the other ALSO unmailable.

This is to protect you, so you're in compliance with anti-spam rules pretty much everywhere.

So if someone is opted out, the duplicate of them is also unmailable.