If you see a “550 5.7.1 [IRR] Too Many Invalid Recipients” error when sending an email, don’t worry! It’s a temporary protection measure from MailChannels, our outbound firewall partner, helping to keep your domain’s reputation strong by preventing your emails from being flagged as spam.
In this guide, we’ll show you exactly what it means, how to fix it, and what to do to prevent it from happening again.
What Does The 550 5.7.1 [IRR] Error Mean?
This error indicates that your account sent messages to a large number of invalid email addresses which means you’re trying to send to recipients that no longer exist or have incorrect formats.
MailChannels automatically pauses outgoing mail to prevent reputation damage and potential blacklisting of your domain or server IP.
Why MailChannels Blocks These Emails
MailChannels uses advanced filtering and behaviour-based algorithms to detect potential spam-like patterns.
Sending to invalid addresses is a strong indicator of:
- Outdated or unverified mailing lists
- Bulk mailings without confirmed recipients
- Misconfigured third-party mailing tools
IMPORTANT: High volumes of invalid recipients can damage your domain’s email reputation, increasing the risk that valid emails will land in spam or get blocked entirely.
How to Fix the Error
To resolve the block and restore your email sending, follow these steps carefully:
1: Clean Your Mailing List
Use email verification tools to identify and remove invalid recipients:
IMPORTANT: Delete all invalid or bounced addresses before resending.
2: Enable Double Opt-In
Implement double opt-in on your contact forms or subscription lists. This means new subscribers confirm their email address before being added, ensuring every contact is valid.
3: Send Only to Active Subscribers
Only send to verified, opted-in addresses. Avoid purchased or scraped lists and re-engage inactive users before sending bulk messages.
4: Wait for Automatic Unblock
Once your mailing list is cleaned, MailChannels typically lifts the block automatically within a few hours once normal sending behaviour resumes.
- Check the content: Remove spammy phrases, suspicious links, or large attachments.
- Authenticate your domain: Add SPF, DKIM, and DMARC records to validate your email.
- Secure your account: Change your password, update your operating system, and run antivirus scans.
- Clean your mailing list: Remove invalid addresses or unengaged contacts.
- Retry sending: Once fixes are applied, retry sending the message.
Tips to Reduce Flags and Maintain a Healthy Sender Reputation
1. Avoid sending bulk messages too quickly. Space out your emails.
2. Regularly verify and update your contact lists.
3. Authenticate your domain with SPF, DKIM, and DMARC records.
4. Monitor bounce rates. Keep them below 2%.
5. Never buy email lists. These lists often contain invalid or spam-trap addresses.
TIP: Monitoring and cleaning your mailing list regularly keeps your email deliverability strong and prevents future blocks.
How to Prevent Future Blocks
- Review your email sending patterns every month.
- Set up SPF, DKIM, and DMARC for your domain to improve trust scores.
- Avoid attachments or links that could appear suspicious.
When to Contact 1-grid Support
If you’ve cleaned your mailing list but your emails are still blocked after 24 hours, provide the following (with screenshots, where possible):
- The full bounce-back message.
- Steps you’ve already tried.
- Provide your sending email address and the timestamp of the error.
- Our Support team will review logs and liaise with MailChannels if necessary to unblock your account.
FAQs
Q: What does “550 Too Many Invalid Recipients” mean?
It means your account has sent too many emails to addresses that don’t exist or are invalid. MailChannels temporarily blocks further sending to protect your email reputation.
Q: How do I unblock my account?
Clean your mailing list using verification tools, remove invalid addresses, and wait a few hours. The block usually lifts automatically once the issue is resolved.
Q: Why is this important for email deliverability?
Invalid recipients hurt your sender reputation, causing legitimate messages to go to spam or get blocked entirely.
Q: Can I prevent this from happening again?
Yes, by regularly cleaning your mailing list, using double opt-in, and avoiding purchased lists.
Q: When should I contact support?
If the block doesn’t lift after 24 hours, or if you continue receiving bounce errors despite list cleanup.
Additional Resources
How to Avoid MailChannels Blocks
MailChannels Error Codes and How to Fix Them
Resolving a MailChannels Spam Block “550 5.7.1” Error
MailChannels FAQs
Everything You Need to Know About Domain Name Systems (DNS)
Updating My Password FAQs
Top 10 Common Email Issues and How to Resolve Them
Setting Up Email in Outlook via Windows Control Panel
How to Set Up Email on Android for Your 1-grid Email Accounts
Settings to Configure Your 1-grid Email Accounts Across Devices
Resolving Email Error Messages When Sending to Gmail Accounts
What is IP Blacklisting?
How Do I Check if My IP is Blacklisted?
SpamTitan: How to Blacklist an Email Address or Domain
What Is Email Spoofing? How It Works and How to Protect Yourself
How to Spot a Scam Email
Email Headers FAQs
Email FAQs
How to Enable DKIM and SPF on Your Mail Domain
Why SSL? The Purpose of Using SSL Certificates
What is a Domain Name Server (DNS)?
How to Update Your Domain’s Nameservers at 1-grid
SpamTitan FAQs
Need Additional Support?
We’re Here to Help:
Preventing emails from being blocked by MailChannels doesn’t have to feel technical with this easy-to-reference guide. Stuck? Contact our Support Team for clarity and guidance (https://1grid.co.za/contact-us/). We’re ready to see how we can help!