Troubleshooting Email Delivery

The following issues can cause an email to be undelivered:

• The recipient is on the Suppression List.
• An authentication failure or an issue with the format of the email message occurred. For example, if the SMTP "From" address is not the same as the "From" address in the email body, the email is rejected. The addresses must match and be an Approved Sender. Refer to your sending application's logs to review any issues.
• Use of multiple addresses in the email From header is discouraged. If you use multiple addresses, it increases the possibility that your mail is placed in a spam folder or discarded (because of Domain-based Message Authentication, Reporting, and Conformance (DMARC) From alignment rules). The performance of your emails is reduced because all addresses have to be authorized as approved senders. A best practice for the SMTP envelope From address is to match the header From address when you submit mail to Email Delivery. If you use mismatched addresses, it reduces the performance of your emails because both addresses need to be authorized as approved senders. Certain future platform features will not be available if you use mismatched addresses.
• Lack of DomainKeys Identified Mail (DKIM).
• View the "dkimSelector" applied to your mail via the Public Logging feature.

DKIM and DMARC can help authenticate your email to help ensure that your emails get delivered to your recipients' inboxes. For more information, see Additional Options to Increase Deliverability.

Refer to Deliverability Best Practices to learn about recommendations that can help lower your email bounce rate, stay off blocklists, lower your complaint rate, and improve your email sender reputation.

If you are unable to resolve the issue, you can go to My Oracle Support and create a service request. See Open a support service request for more information.

Refer to Configuring SMTP Connection for a list of regional endpoints to establish SMTP connections for sending.

• If you are encountering TLS errors when attempting to integrate Postfix with Email Delivery, ensure that the following setting is removed from the Postfix main.cf file, as it has been deprecated:

  smtp_use_tls = yes

• Use the following setting instead to turn on TLS:

  smtp_tls_security_level = may

  Using this setting, the Postfix SMTP server announces STARTTLS support to remote SMTP clients, but does not require that clients use TLS encryption.

• If you want to enforce the use of TLS, so that the Postfix SMTP server announces STARTTLS and accepts no mail without TLS encryption, use the following setting:

  smtp_tls_security_level = encrypt

For more information, see Postfix TLS Support.

To activate your DKIM key, you must provision a DNS CNAME record at this location in your Email Domain's DNS:

<selector>._domainkey.<email-domain>

However, different DNS providers have different user interfaces to specify the location of a DNS record. Some user interfaces accept the full DNS path by default and these will work well. Some user interfaces are relative to the zone by default, so if you paste in the entire string without the trailing period, the user interface will provision the wrong location and that will leave your DKIM key in a "Needs Attention" state. Avoid entries like this:

<selector>._domainkey.<email-domain>.<zone-name>

If your Email Domain is the same as your DNS zone name and if your provider only accepts a zone-relative name, use this DNS CNAME location:

<selector>._domainkey

If your Email Domain is in a subdomain of your zone and if your provider only accepts a zone-relative name, use this DNS CNAME location:

<selector>._domainkey.<subdomain>

For Email Delivery limits issues, see Email Delivery Service Capabilities and Limits and Service Limits for a list of applicable limits and instructions for requesting a limit increase.