List the mailboxes, websites, billing systems and devices that send for your domain. Confirm which server or application will relay through the purchased filtering service. Do not change every application's SMTP settings until the service's supported authentication and relay requirements are clear.

1. Open the outgoing-filter service and obtain its documented relay destination, port, encryption and authentication settings. Use the service-specific values rather than generic SMTP examples.
2. Ask the authorised mail administrator to configure the supported outbound route. Restrict permitted senders or source addresses, and never enable an open relay.
3. Update SPF and any related authentication configuration for the approved sending path. Preserve other legitimate senders and keep one coherent SPF policy for the domain.
4. Check DKIM and DMARC alignment using a real message received externally. A visible From address is not necessarily the domain used by every authentication mechanism.
5. Send a small test from webmail and each important application. Confirm the message passes through the filter and reaches the recipient.
6. Monitor logs, rejection reasons and volume before enabling the route for normal production traffic.

Use the filtering log to identify the authenticated account or source application, recipient, time and reason. A sudden burst of messages may indicate a compromised password, abused contact form or infected website. Pause the affected sender, investigate the source and rotate exposed credentials before requesting removal of a restriction.

Do not solve a block by routing the same suspicious traffic around the filter. Correct the message content, authentication or account problem and test again with a small legitimate sample. Large repeated retries can make an incident harder to resolve.

Keep recipient lists permission-based, remove invalid addresses and provide appropriate unsubscribe controls for marketing mail. Separate ordinary mailbox use from bulk campaigns. When asking support for help, share sanitised message identifiers and rejection text, not mailbox passwords or a complete customer mailing list.

• Setting up incoming email filtering without interrupting mail
• Planning email archiving, retention and authorised searches
• Troubleshooting email delivery, spam placement and authentication records
• Connecting Google Workspace securely and fixing authentication failures

• SpamExperts email services
• Gmail Senders