Suppressions

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The suppression list contains email addresses that should not receive emails. This includes bounced addresses and spam complaints.

Why Suppressions Matter

Sending to suppressed addresses harms your sender reputation:

  • Bounces: Continued attempts to invalid addresses signals spam behavior
  • Complaints: Ignoring spam reports can get your domain blacklisted

toSend automatically manages your suppression list to protect your deliverability.

Viewing Suppressions

Go to Suppressions in your dashboard to see all suppressed addresses with:

  • Email address
  • Type (Hard bounce, Soft bounce, Complaint or Invalid)
  • Reason
  • Last activity

Suppression Types

Bounced

Email addresses that bounced. A hard bounce (permanent failure) blocks sending to the address for 60 days. A full mailbox blocks it for 24 hours. Any other soft bounce (temporary failure) blocks it for 2 hours, and only once the address has soft-bounced twice within 2 hours, so a single temporary failure never stops your next email. Content-related bounces (ContentRejected, MessageTooLarge, AttachmentRejected) never block the address.

Bounce TypeDescription
GeneralGeneric permanent failure
MailboxFullRecipient’s mailbox is full
ContentRejectedEmail content was rejected
SuppressedPreviously bounced address

Temporary rejections caused by the receiving server blocking the sending IP on a public blocklist are not suppressed. The message is logged as bounced and the next send is attempted normally, since the address itself is fine.

Complained

Email addresses where the recipient clicked “Report Spam” or “Mark as Junk” in their email client. Sending to that address from the same domain is blocked for 180 days.

Validation Suppressed

Addresses that failed email validation checks before sending.

Filtering Suppressions

By Type

  • Bounced: Show only bounced addresses
  • Complaint: Show only spam complaints
  • Invalid address: Show only addresses that failed validation

By Domain

View suppressions for a specific sending domain.

Search for a specific email address.

Automatic Suppression

toSend automatically adds addresses to your suppression list when:

  1. Hard bounce: Permanent delivery failure (invalid address, domain not found)
  2. Soft bounce: Temporary delivery failure. A full mailbox is held for 24 hours; other temporary failures are held for 2 hours after a second one within 2 hours
  3. Spam complaint: Recipient reports email as spam

Sending to Suppressed Addresses

If you attempt to send to a suppressed address:

  • The email will be blocked
  • If every recipient is suppressed, it will appear in your logs with status “Suppressed”; otherwise only the suppressed recipients are skipped
  • A bounced webhook event is sent for each skipped recipient
  • No email will be sent to protect your reputation

Best Practices

  • Monitor bounce rates: High bounce rates (>4%) indicate list quality issues
  • Clean your lists: Remove inactive subscribers regularly
  • Use double opt-in: Confirm email addresses before adding to your list
  • Honor unsubscribes: Remove unsubscribed users promptly