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Global suppression

Global Suppression is a safety net within MX18’s email infrastructure that protects all senders across the platform from delivering to invalid or harmful email addresses. It’s an automated, intelligent mechanism to help maintain high deliverability and reduce ISP complaints.

What is global suppression?

Global Suppression refers to a centralized suppression list maintained by MX18, called the Global Suppression List (GSL). This list is populated based on repetitive bounce and failure patterns observed across all accounts on the platform.

If an email address repeatedly fails due to hard bounces (especially 5.X.X class errors), it is automatically added to the GSL.

Example scenarios that trigger global suppression:

  • 550 5.1.1 User unknown
  • 550 5.4.1 No mailbox here by that name
  • 554 5.7.1 Relay access denied

How MX18 manages the GSL

  • MX18 dynamically updates the Global Suppression List based on recurring bounce signals across accounts
  • Addresses added to GSL are automatically blocked from delivery across all customer accounts
  • Periodically, we recheck GSL entries using internal validation tools:
  • If the address responds as valid, it is removed from GSL
  • The address remains in the original account’s account-based suppression list for added safety

This layered approach ensures that you’re not re-trying known bad addresses and also helps prevent unnecessary loss of potential good contacts.

Can I opt out?

Yes — MX18 allows account-level opt-out from the Global Suppression List.

However, we strongly discourage disabling GSL as it:

  • Exposes your account to known invalid or dead email addresses
  • Increases bounce and complaint rates
  • May affect your IP/domain reputation and inbox placement

To discuss opt-out, contact support@mx18.com

Need help?

If you want to audit your GSL matches or discuss suppression logic:

  • Email us at support@mx18.com
  • We can help you review how suppression events are being managed across your account