Suppression List:
Suppression list for email outreach: which addresses to add, how long to keep them, what Gmail and the law require. + A template with 6 suppression categories.
A suppression list is a list of addresses that must never receive email from any of your campaigns. It includes people who unsubscribed, marked you as spam, hard-bounced or asked you to stop writing. The suppression list is checked before every send and protects you from fines, complaints and a damaged domain reputation.
At the end of this article you'll find a suppression list template with 6 categories, each with its source, retention period and blocking level. Copy it into a spreadsheet or your CRM.
At a glance: suppression lists in numbers
| Fact | Value | Source |
|---|---|---|
| Time to process an unsubscribe for Gmail | within 48 hours | |
| Mail.ru unsubscribe requirement | without delay and without logging in to a website | Mail.ru |
| Obligation under Russia's Advertising Law | “immediately stop” sending at the recipient's request | 38-FZ, art. 18 part 1 |
| Fine for a company in Russia for advertising over telecom networks in breach of art. 18 | RUB 300,000 – 1,000,000 | Russian Administrative Code, art. 14.3 part 4.1 |
| Gmail complaint threshold | below 0.1%, never 0.3% |
Why you need a suppression list
Without one, the same person gets your emails again: from a new campaign, from a different mailbox or after you import a fresh list. To them it's spam, and they'll click “Report spam”.
A suppression list does three jobs:
- Legal. Russia's Advertising Law requires you to stop sending immediately at the person's request, and the sender must prove consent was given (38-FZ, art. 18).
- Reputation. Every complaint brings you closer to Gmail's 0.1% threshold, after which deliverability drops.
- Technical. Repeated sends to non-existent addresses raise your bounce rate and lead to spam traps.
Who to add to the suppression list
The rule is simple: if a recipient has made it clear, explicitly or technically, that you shouldn't email them, the address goes on the list immediately.
- Unsubscribed via a link or the List-Unsubscribe header.
- Clicked “Report spam”.
- Replied “don't email me”, “remove me”, “not interested, stop writing”.
- Hard-bounced (code 5.1.1, 5.1.2, 5.2.1).
- Withdrew consent to the processing of personal data.
- The company is already your client, partner or competitor — they don't need cold emails.
Don't add soft bounces or “out of office” auto-replies. These are temporary: it's better to pause the address.
Suppress by address or by domain
In B2B, one address is often not enough. If a company's director wrote “we don't need this” and a week later their deputy gets your email, it looks pushy.
| Level | When to use | Example |
|---|---|---|
| Address | Unsubscribe, complaint, hard bounce, personal request to stop | ivan@company.com |
| Company domain | Refusal on behalf of the company, clients, partners, competitors | @company.com |
| Your own domains | So sequences don't go to your own addresses and test mailboxes | @your-company.com |
Never suppress free mailbox domains (gmail.com, mail.ru, yandex.ru) as a whole — only specific addresses.
How to maintain a suppression list
- One list for the whole company. Not a separate one per campaign or salesperson, or the address will come back from another mailbox.
- Check before every send, including follow-ups in a sequence that's already running.
- Check on every list import: suppressed addresses must not get into a campaign even if they're in the new file.
- Keep indefinitely for unsubscribes, complaints and requests to stop. Store the minimum: address, date and reason.
- Automate additions: unsubscribes and hard bounces should be added without human involvement, and a salesperson adds “don't email me” replies the same day.
Gmail expects unsubscribes to be processed within 48 hours, Mail.ru without delay, and Russia's Advertising Law immediately. Follow the strictest requirement.
How to offer an opt-out in a cold email
A cold email doesn't need an unsubscribe button in the footer, but the way to opt out must be obvious. Three options work:
- A line at the end of the email: “If this isn't relevant, just reply ‘no’ and I won't write again.”
- An unsubscribe link that works instantly, with no login or confirmation.
- A List-Unsubscribe header so the mailbox provider shows its own unsubscribe button. Mail.ru recommends it.
Better for someone to unsubscribe than to click “Report spam”: an unsubscribe doesn't hurt your reputation, a complaint does.
Suppression list template: 6 categories
Copy the structure into a spreadsheet or CRM. The list itself only needs four fields: address or domain, category, date, added by.
| # | Category | Source | Level | Retention | Can it be reversed |
|---|---|---|---|---|---|
| 1 | Unsubscribe | Link or List-Unsubscribe | Address | Indefinitely | Only if the person writes to you first |
| 2 | Spam complaint | Mailbox provider FBL, sending stats | Address | Indefinitely | No |
| 3 | Request to stop | Reply to an email | Address; domain if refused on behalf of the company | Indefinitely | Only if the person writes to you first |
| 4 | Hard bounce | Code 5.1.1, 5.1.2, 5.2.1 | Address | Indefinitely | No: the address may become a trap |
| 5 | Withdrawal of consent to data processing | Written request | Address | Indefinitely, with minimal data | Only with new consent |
| 6 | Business exclusions | Clients, partners, competitors, your own domains | Domain | While relevant, review quarterly | Yes, by team decision |
Keep soft bounces and auto-replies on a separate “paused” list with a return date, not on the suppression list.
Frequently asked questions
What is a suppression list in email outreach?
It's a list of addresses and domains you must not email. It's checked before every send so you don't email people who unsubscribed, complained or don't exist.
How is a suppression list different from a blocklist?
You maintain the suppression list: these are addresses you don't email. A blocklist is maintained by mailbox providers and organizations like Spamhaus: these are senders whose email gets blocked.
How quickly should an address be added to the suppression list?
Immediately. Russia's Advertising Law requires stopping at the recipient's request right away, and Gmail allows no more than 48 hours to process an unsubscribe.
How long should addresses stay on the suppression list?
Unsubscribes, complaints, requests to stop and hard bounces — indefinitely, or the address will come back with a new list. Review business exclusions like clients and partners quarterly.
Do I need a suppression list for cold outreach?
Yes, even more than for subscriber email. Cold lists often overlap, and without a suppression list someone who said no will get an email from your next campaign.
Should I add addresses with an auto-reply to the suppression list?
No. An “out of office” auto-reply or a soft bounce is temporary. Pause the address until the return date in the auto-reply.
Sources
- Russian Federal Law 38-FZ “On Advertising”, art. 18 (ConsultantPlus) (in Russian).
- Russian Administrative Code, art. 14.3 (ConsultantPlus) (in Russian).
- Google: Email sender guidelines FAQ — 48 hours to process an unsubscribe.
- Mail.ru: general mailing rules (in Russian).
This is not legal advice: agree how suppression data is stored with your lawyer. If you email recipients in the US or EU, CAN-SPAM and GDPR apply as well.