How did my recipient land on the Suppression List?

The suppression list is a list that contains email addresses that are permanently excluded from your email lists and will not receive future emails. The most common way a recipient lands on the Suppression List is because of a hard bounce. 

A hard bounce is an email message that has been returned to the sender because the recipient's address is invalid. A hard bounce might occur because the domain name doesn't exist or because the recipient is unknown.

Here are some other ways that a recipient might end up on your Suppression List. 

Spam complaint - Subscribers that flag an email as spam are immediately added to the suppression list.

Manually Added - At times a partner may decide to manually add recipients to the suppression list using Settings > Suppression List

Unsubscribe - If the partner has elected to add any unsubscribes to the suppression list in Settings > Company Profile, then unsubscribed contacts will appear in the suppression list. 

Soft bounce - A soft bounce is an email message that makes it to the recipient's mail server, but is bounced back as undelivered before it gets to the intended recipient. This might happen because the recipient's inbox is full and it may be deliverable at a later time. After three delivery attempts, it will become a hard bounce. Here are some examples of soft bounces.

  • Transient bounce - A transient bounce is often generated by the sender's email server; this indicates that a message could not be delivered, but that the server is still trying to do so. Usually, a transient bounce can be safely ignored. You might receive this message: Warning: message still undelivered after 4 hours. Will keep trying until message is 2 days old.
  • Address Change - An Address Change response means a recipient has changed their address and is sending an automatic reply to notify senders of their new address.
  • Auto-Reply - Auto-Replies (generally in the form of an out-of-office notice) are usually sent by a recipient's email client. Unlike bounces, these indicate that an email recipient is temporarily unavailable. These notifications are useful when sending time-sensitive information to recipients, as they serve to alert you that the recipient may not see it until later. These can otherwise be safely ignored.
  • Challenge/Response - A Challenge/Response reply is a message sent by special filtering software installed by the recipient designed to accept messages from only senders they know. This type of filter automatically sends a reply with a challenge (a question or required action) to the sender of the email. If the challenge is not completed correctly, the message is not delivered.
  • DNS failure - The email server is temporarily unable to deliver your message to an email address because of a DNS problem.
  • Email blocked - Indicates that the recipient's email server is blocking email from your email server. You may see the following messages returned to you:
    • - 550 Message REFUSED by peer
    • - 552 Blocked by filters
  • Mailbox is full - The email server is temporarily unable to deliver your message to the recipient email address because the recipient's email box is full.


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