Ask Al: Can we email the opt-outs?

A friend sent me the following question the other day: “Hi Al! How are you? I have one client who wants to send an email to more than 600,000 recipients who have already opted-out. I’m worried that this is a very bad idea, but I do not see a lot of documentation out there. What do you think?”

Thanks to my friend for sharing this! I’m not going to name them, to help prevent them from receiving any fallout for seeking my advice.

Sending email to 600,000 unsubscribed recipients comes with significant legal and deliverability risks. It will cause problems. I would not even consider it, to be honest.

Here’s a breakdown of the potential problems for both transactional and marketing messages. I’ll be a bit brief; be sure to consult your own legal counsel and/or deliverability expert for more specific, customized guidance on this issue.

Potential Legal Issues

The legality of emailing unsubscribed users depends on the type of message and applicable laws like CAN-SPAM (U.S.), GDPR (EU), CASL (Canada), and others. Remember that I’m not a lawyer. This is just my layperson’s interpretation. Consult a lawyer.

If you send a marketing (promotional) message to those recipients, you’re likely in violation of:

• CAN-SPAM (U.S.): You are legally required to honor opt-outs. Sending marketing emails to unsubscribed users can result in fines of up to $50,120 per violation.
• GDPR (EU): Requires explicit opt-in for marketing. Sending to unsubscribed users can lead to hefty fines (up to €20 million or 4% of annual global revenue).
• CASL (Canada): Sending without proper consent could result in fines up to CA$10 million.
• Other Countries: Many jurisdictions impose strict opt-in rules, and violating them can lead to legal action. Keep in mind that for all of these laws; no essentially means no. It doesn’t mean “you get at least one more bite at the apple later.”

If you were to send transactional (non-promotional emails), it gets trickier.

• CAN-SPAM: Allowed, as long as it is genuinely transactional (e.g., password resets, account updates). However, adding marketing content could make it non-compliant.
• GDPR & CASL: Even transactional emails require a legal basis for processing data. If the recipient is no longer a customer, sending might be illegal.
• Risk of complaints: Even if legal, recipients may still report your email as spam, leading to deliverability problems, blocklistings and sender reputation issues. This is a big one; even if legal compliant, your messages and reputation are still subject to feedback from recipients, and sending mass email to a large group of previously unsubscribed recipients will garner you lots of negative feedback.

Deliverability Issues

Even if the email is legally permitted, mailbox providers (Gmail, Yahoo, Microsoft, etc.) have their own rules. You will not be exempt from spam filtering or sender requirements, and those sender requirements include permission and require low spam complaint rates.

If you send a marketing (promotional) message to those recipients, you’re going to run into:

• High Spam Complaints: Users unsubscribed for a reason. Sending again may trigger spam complaints, tanking your sender reputation.
• Blocklistings: Large-scale complaints could land your IP or domain on anti-spam blocklists like Spamhaus, Spamcop, SURBL and others. (Email addresses churn; long unsubbed addresses will contain a significant % of dead addresses, some recycled into spamtraps, and blocklists notice large mailings to significant numbers of spamtrap addresses.)
• Low Engagement: Sending to unengaged users results in poor open rates, leading to emails going straight to the spam folder. It’s
• Bounces & Invalid Addresses: As mentioned above: Over time, many unsubscribed addresses may become invalid. High bounce rates can cause email providers to throttle or block your emails.

If you were to send transactional (non-promotional emails), you won’t magically be in the clear.

• Spam Filtering Risks: If the message is perceived as irrelevant or aggressive, users will mark it as spam en masse, harming future deliverability.
• ISPs May Still Block: Even transactional messages can be filtered if they resemble marketing or if sent in bulk to disengaged users.
• User Frustration: Even if "legal," an unwanted email may still trigger complaints, harming your brand reputation. This is not a way to make friends.

The Bottom Line

Sending marketing emails to unsubscribed users is illegal in many jurisdictions and extremely risky for deliverability. Transactional emails must be genuinely necessary and carefully worded to avoid looking like marketing -- and you're still at risk, because mailbox provider mandated sender requirements still apply, and do not make explicit exceptions for this scenario.

There might be a reason that you have to send a legally mandated email message to your entire userbase, including to those who have unsubscribed from emails previously. Email/messaging anti-abuse working group M3AAWG, whose members include many mailbox providers, has provided guidance on how to plan and execute legally mandated mailings. But much of that guidance is a bit high level, and assumes that email is the best way to make this mandated notification. It might not be.

Best to consult with deliverability experts who have experience with this type of thing.