What keywords can I use to filter reply messages for unsubscribe requests?
Matthew Whittaker
Co-founder & CTO, Suped
Published 4 Jun 2025
Updated 19 Aug 2025
6 min read
Managing email unsubscribe requests is crucial for maintaining a healthy sender reputation and ensuring compliance. While the List-Unsubscribe header is the preferred and most reliable method for recipients to opt out, some users still reply directly to messages with their unsubscribe intentions. These replies, often sent to a no-reply address, can accumulate quickly, making it challenging to identify and process actual opt-out requests efficiently. This is where keyword filtering becomes essential.
Relying solely on an unsubscribe link isn't always enough because some users, especially those frustrated or wary, might bypass it and reply instead. Promptly identifying these reply-based unsubscribe requests, even if they're not formatted as a standard click, is a critical step in maintaining good email hygiene and avoiding potential blocklisting issues. Neglecting these replies can lead to ongoing complaints, which can severely impact your deliverability.
The goal is to automate the detection of these keywords within reply messages, so you can unsubscribe the user from your mailing list. This proactive approach helps reduce spam complaints, improve your sender reputation, and ensures you remain compliant with regulations like the CAN-SPAM Act, which mandates honoring opt-out requests promptly. Ensuring deliverability means understanding all the ways recipients might try to stop receiving your emails.
Identifying common unsubscribe keywords
When building a comprehensive keyword list for filtering unsubscribe requests, it's important to start with the universally recognized terms. These are the words most commonly used by recipients and are often suggested by telecommunication carriers and email service providers as standard opt-out commands. These keywords form the backbone of your filtering system, ensuring you catch the most straightforward requests.
Standard English terms: STOP, UNSUBSCRIBE, CANCEL, QUIT, END, OPT-OUT, REMOVE.
Common variations: UNSUB, UNSTOP, NO, STOPALL.
Foreign language equivalents: CANCELAR, DESUSCRIBIRME (Spanish); AIDE (French); HILFE (German).
These standard keywords are widely recognized in the email and SMS marketing industry. For instance, telecommunication providers like Twilio often require these specific keywords for automated opt-out processing in SMS, and the principle extends to email replies. Including these in your filter ensures you capture compliant opt-out requests.
Expanding your keyword list for implicit intent
Beyond the standard terms, many recipients use more informal or frustrated language to express their desire to stop receiving emails. To catch these, your filter needs to include a broader range of keywords that convey implicit unsubscribe intent. This expanded list can significantly reduce the number of recipients who might otherwise continue receiving unwanted mail, potentially leading to spam complaints or a negative impact on your sender reputation.
Explicit intent with variations: "please unsubscribe me", "take me off", "remove me from your list".
Keywords indicating unwanted mail: "spam", "junk", "unwanted", "undesired", "no consent", "never signed up", "not interested".
Terms expressing annoyance/discontinuation: "annoying", "block", "bombarded", "bothersome", "enough", "excessive", "discontinue", "no longer", "no more", "quit emails".
It's also beneficial to consider common misspellings or typos of these keywords. People often type quickly on mobile devices, leading to minor errors. Including variations like "unsubcribe" or "stop email" can help you capture a wider range of requests. Regularly reviewing your reply inbox can help you identify new terms or misspellings that are commonly used by your audience.
Handling tricky replies and avoiding false positives
While broadening your keyword list is good, it also introduces the risk of false positives. Auto-replies, out-of-office messages, and general queries can contain words that might accidentally trigger an unsubscribe filter if not carefully managed. You want to avoid inadvertently unsubscribing engaged users, which can hurt your list size and engagement metrics.
Identifying auto-replies
Keywords often found in auto-replies include: "vacation", "out of office", "will be back", "away", "auto-reply", "delivery failed", "bounce".
These messages typically indicate temporary unavailability or technical issues, not a desire to unsubscribe.
Mitigating false positives
Implement rules to prioritize explicit unsubscribe keywords or combine multiple keywords within a reply for a higher confidence score. For example, require both "stop" and "email".
Regularly review a sample of filtered messages that trigger the unsubscribe action to ensure accuracy. Human review remains a vital part of the process.
To minimize false positives, it's also helpful to look for specific email content keywords that indicate a non-unsubscribe intent. For instance, if a reply contains "looking for" or "question about", it's likely a legitimate inquiry, even if it also includes a word like "end" in a different context. Contextual analysis, even if basic, is key to accurate filtering.
A robust system for handling replies should include a combination of automated filtering and human oversight. While automation can handle the bulk of requests, manual review for complex cases or suspected false positives is invaluable. This hybrid approach helps ensure that you honor all unsubscribe requests while retaining genuinely interested subscribers, especially important with recent enforcement from Gmail and Yahoo.
Best practices for reply management
To ensure effective management of reply-based unsubscribe requests and maintain good sender hygiene, there are several best practices to follow. These practices help streamline the process, reduce manual effort, and protect your sender reputation from unnecessary spam complaints or blocklist issues.
Reply mail management
Set up a dedicated reply-to address to capture all responses, rather than using a generic "no-reply" address. This makes it easier to centralize and process replies. Configure your system to automatically manage these replies, categorizing them based on keywords or other indicators. Major providers like Salesforce often provide features for this. This also ties into how email replies and 'no-reply' addresses affect deliverability.
Compliance requirements
The CAN-SPAM Act requires that all unsubscribe requests be honored within 10 business days. Automated keyword filtering helps you meet this requirement efficiently. Ensure your filtering system is robust enough to process these requests quickly and accurately. This is why 'reply to unsubscribe' is an acceptable option.
Regularly monitor your email blocklist (or blacklist) status. A sudden increase in spam complaints, which can result from unhandled unsubscribe requests, often leads to your domain or IP being placed on a blocklist. Proactive monitoring allows you to identify issues early and take corrective action, safeguarding your deliverability. Maintaining a clean list also involves understanding what happens when your domain is on a blocklist.
Final thoughts on managing unsubscribe replies
Effectively filtering reply messages for unsubscribe requests is a dynamic process that requires ongoing attention and adaptation. While automated systems are powerful, they are most effective when guided by a comprehensive keyword list and regular human review. By embracing both explicit and implicit unsubscribe signals, you can maintain a cleaner email list, ensure compliance, and protect your valuable sender reputation from potential damage.
Remember, every unsubscribe request, regardless of how it's conveyed, is an opportunity to improve your email program. Honoring these requests promptly and accurately demonstrates respect for your subscribers and helps build trust, leading to better overall email deliverability and engagement.
Views from the trenches
Best practices
Maintain a comprehensive keyword list, including standard opt-out terms and their common variations and misspellings.
Use a dedicated reply-to address for all outgoing emails to centralize incoming replies and streamline filtering.
Regularly review a sample of filtered unsubscribe requests to identify new keywords and refine your filter rules.
Prioritize honoring unsubscribe requests promptly to comply with regulations and preserve sender reputation.
Common pitfalls
Over-relying on only standard keywords, missing many implicit unsubscribe requests from frustrated users.
Neglecting to filter for foreign language equivalents, leading to unaddressed unsubscribe requests from international recipients.
Failing to review filtered messages, which can result in accidentally unsubscribing active and engaged subscribers.
Using a 'no-reply' address that doesn't route replies, causing all unsubscribe requests via reply to be missed.
Expert tips
Consider using regular expressions in your filtering system to catch variations of keywords and common misspellings more efficiently.
Categorize inbound replies not just for unsubscribes but also for out-of-office, bounced, or general inquiries to manage your inbox effectively.
Automate the process of moving identified unsubscribe replies to a dedicated folder for easy review and processing, if direct unsubscribing isn't possible.
Integrate your reply filtering with your CRM or email service provider to automate the actual unsubscribe action as much as possible.
Marketer view
Marketer from Email Geeks says we should try to unsubscribe or suspend everyone who replies, except for people who use non-unsubscribe keywords, to simplify the process. They suggest using a separate reply-to address to distinguish human replies from auto-replies.
2023-02-02 - Email Geeks
Marketer view
Marketer from Email Geeks says they have a list of keywords for filtering unsubscribe requests that includes terms such as 'annoying', 'block', 'bombarded', 'bothersome', 'no consent', and 'unsolicited'.
