Unsubscribed leads still receiving emails

Hello,

I've set up a very straightforward engagement program in Marketo. People are added to the engagement program (Stream 1) if they are a member of a specific smart list setup in the Lead Database and if their email address doesn't contain the company's domain name.

I have another smart campaign which removes people from the program if they are a member of an exclusion list. The flow step would set their status to "Not in program" for the engagement program.

The email program under the engagement program all have smart campaigns to control the Email Send and track progression. The Send Email batch campaign checks to see if the lead is a member of the engagement program in Stream 1. If so, then the first email is sent. The remaining emails are set up similarly.

After the first email went out, we discovered that out of 4072 emails sent, 26 of them went to leads who were marked as unsubscribed. These leads are not duplicates or anything like that. I looked at the lead records and unsubscribed is ticked.

I'm trying to understand why this might have happened because Marketo should have automatically not sent these people emails if their lead records who them as unsubscribed. Any help or guidance would be appreciated. For now the only solution I have in mind is to include an "Unsubscribed=False" filter on the Send Email campaigns to ensure the emails only go out to people who are not unsubscribed.

Thanks!