A frequent question for the OCI Email Delivery team is why is a specific email address keeps getting suppressed.
An email suppression is when someone attempts to send to an email address and that address either hard bounces or is reported as spam (ex. using Outlook’s spam button.) The email is then added to the sender’s suppression list and because of that action, they can no longer send to the address for as long as it remains on the list.
Let’s expand on those reasons:
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Hard bounce: A receiving mail server sends back a 500 error bounce code message that the address can’t be delivered to as intended. Typically, this error happens when the address is misspelled or the associated mailbox doesn’t exist anymore/is no longer active.
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Complaints: When a user clicks the spam button in their browser to complain about the email. This action ensures that future emails from that sender are no longer sent to the complaining address.
For Oracle senders who are sending to internal distribution lists through Oracle Cloud Infrastructure (OCI) Email Delivery, we have the following other explanations:
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An individual address has hard bounced on the distribution list, unsubscribing the entire distribution list. For that reason, we don’t recommend sending to distribution lists through OCI Email Delivery (or any provider).
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The sender hasn’t set up Domain Key Identified Mail (DKIM) on their sending domain and is attempting to send emails to other email addresses through a trusted shared IP pool. Access to such a pool is done by OCI Email Delivery approval only.
You can find the exact reason for the initial hard bounce in public logging in the Oracle Cloud Console, if enabled by the tenancy’s admin. If you haven’t set up service logs, do that first and then remove the suppression from your OCI Email Delivery suppression list. If the problem persists, you can see the error in your logs the next time you attempt to send to that address.
Can suppressed emails be mailed to again?
After the user removes the suppression, they can be emailed again, but only if any underlying issues, such as misspelling, have been resolved first. Legitimate hard bounces sent to addresses that truly don’t exist or result in complaints should always remain suppressed. By not adhering to this practice, the sender opens themselves up to future domain and IP blacklisting. This problem results in no email getting delivered from the sender domains, a potential suspension of the account from the OCI Email Delivery team, or both.
The suppression mechanism is critical in protecting the reputation of all emails from an email service provider. Repeated attempts to send to an invalid recipient result in the sender being considered a spammer by various anti-spam technologies. As a result, no opt-out option from the suppression mechanism exists.
How to avoid suppression
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For internal Oracle senders sending to internal Oracle addresses, ensure that the sending domain has a valid DKIM record with OCI Email Delivery. Not having this record in place can cause the immediate suppression of the sending address.
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Don’t use OCI Email Delivery to send to distribution lists, if possible.
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If distribution lists must be used, ensure that the lists are curated by a constantly updated database.
Final thoughts
Suppressions are a necessary failsafe to help senders maintain clean databases and avoid bad sending reputations. Before contacting support to answer why a specific address is being suppressed, use this guide as a review and gain a better understanding of your sending practices.
For more information on the concepts in this post, see the following resources: