--- title: Custom Bounce Domains and SPF Authentication description: The Custom Bounce Domain is how SPF is implemented with SocketLabs. This is done without needing to adjust your existing SPF record. --- [Skip to content](https://help.socketlabs.com/docs/custom-bounce-domains#main-content) English Show submenu for translations [Contact us](https://help.socketlabs.com/docs/kb-tickets/new?hsLang=en) [![SocketLabs logo](https://help.socketlabs.com/hs-fs/hubfs/Logos/SocketLabs%20logo.png?width=243&height=70&name=SocketLabs%20logo.png)](https://www.socketlabs.com/) Open main navigation Close main navigation - English Show submenu for translations - [Contact us](https://help.socketlabs.com/docs/kb-tickets/new) SocketLabs is here to help! - There are no suggestions because the search field is empty. 1. [Help Center](https://help.socketlabs.com/docs?hsLang=en) 2. [DNS Authentication](https://help.socketlabs.com/docs/dns-authentication?hsLang=en) 3. [SPF and Custom Bounce Domain](https://help.socketlabs.com/docs/dns-authentication?hsLang=en#spf-and-custom-bounce-domain) # Custom Bounce Domains and SPF Authentication ## The Custom Bounce Domain is how SPF is implemented with SocketLabs. This is done without needing to adjust your existing SPF record. ### Bounce Addresses Email messages contain two "from" addresses, the Return Path and the Friendly From address.  The return-path address is also known as the Mail From, Envelope From, 5321.from, or the **Bounce address**. This address is not shown to the recipient and is the designated email address where bounced messages and other feedback is sent. In this article, we'll refer to it as the return-path. The Friendly From address is also known as the Display From or 5322.from. This is the address that is shown to a recipient. The return-path address is what a receiving server checks to verify the SPF record. The receiving server does **not** check the friendly-from domain, so an SPF record on the friendly-from is not necessary. ### **Custom Bounce Domain Setup** **1. Log into your DNS provider for your sending domain.** **2. Create a subdomain.**  **3. Point a CNAME for that subdomain to tracking.socketlabs.com.** To set up the custom bounce domain for example.com, the following CNAME record would need to be configured: ``` email.example.com CNAME tracking.socketlabs.com ``` This record tells DNS systems that when looking up email.example.com, they should redirect and look at the records for tracking.socketlabs.com. Modifications to DNS settings can take up to 48 hours to propagate, but generally will propagate within minutes. ### **Custom Bounce Domain Setup for Sub-Clients** If your organization provides services to sub-clients, we support white-labeling the DNS records you ask for sub-clients to create. This requires each sub-client to create a CNAME record which references the CNAME record you created that points to SocketLabs.  ``` bounces.customerexample.com CNAME email.example.com CNAME tracking.socketlabs.com ``` ### Return-Path and Custom Bounce Domain: Examples #### Sending without Custom Bounce Domain set up in SocketLabs If you do not set up any custom bounce domains, we will use email-od.com as the default value. Each server may only have a single default value configured. This is a message that does not have any custom bounce domains set up: ``` Return-Path: <9ff5.82.c37d01248d0c5.847f6806d0589331@email-od.com>From: Your Company via email-od.comTo: your.recipient@example.com ``` In this example, the receiving server will look at the return-path domain and will look for the SPF record belonging to email-od.com.  If you do not set up your custom bounce domain, your recipients are likely to see an additional "via email-od.com" in the sender details of an email. #### Sending with Custom Bounce Domain set up in SocketLabs If you have set up your custom bounce domain (in this case, bounces.something.example) to point to tracking.socketlabs.com, you will no longer see "via" and will have successfully set up SPF authentication: ``` Return-Path: <8c229047f6aa6add74c68806d0589331@bounces.example.com>From: Your Company To: your.recipient@example.com ``` In this example, the receiving server will look at the return-path domain, see that bounces.something.example points to tracking.socketlabs.com, and will successfully authenticate. ### Multiple Custom Bounce Domains You can add multiple custom bounce domain entries in the SocketLabs Control Panel. We will automatically match your from address to the appropriate custom bounce domain entry. If no match is found, we will use either your selected default custom bounce entry *or* we will use email-od.com as the default.                 - [Fundamentals](https://help.socketlabs.com/docs/fundamentals?hsLang=en#main-content) - [StreamScore](https://help.socketlabs.com/docs/fundamentals?hsLang=en#streamscore) - [Reports](https://help.socketlabs.com/docs/fundamentals?hsLang=en#reports) - [Frequently Asked Questions](https://help.socketlabs.com/docs/fundamentals?hsLang=en#frequently-asked-questions) - [Advanced](https://help.socketlabs.com/docs/advanced?hsLang=en#main-content) - [Security](https://help.socketlabs.com/docs/advanced?hsLang=en#security) - [DNS Authentication](https://help.socketlabs.com/docs/dns-authentication?hsLang=en#main-content) - [DKIM](https://help.socketlabs.com/docs/dns-authentication?hsLang=en#dkim) - [SPF and Custom Bounce Domain](https://help.socketlabs.com/docs/dns-authentication?hsLang=en#spf-and-custom-bounce-domain) - [Deliverability](https://help.socketlabs.com/docs/deliverability?hsLang=en) - [For Developers](https://help.socketlabs.com/docs/for-developers?hsLang=en#main-content) - [Event Webhooks](https://help.socketlabs.com/docs/for-developers?hsLang=en#event-webhooks) - [Integrations](https://help.socketlabs.com/docs/integrations?hsLang=en#main-content) - [Languages and Frameworks](https://help.socketlabs.com/docs/integrations?hsLang=en#languages-and-frameworks) - [Mail Servers](https://help.socketlabs.com/docs/integrations?hsLang=en#mail-servers) - [Web Clients and Plug-ins](https://help.socketlabs.com/docs/integrations?hsLang=en#web-clients-and-plug-ins) - [Mail Clients](https://help.socketlabs.com/docs/integrations?hsLang=en#mail-clients) - [Marketing Tools](https://help.socketlabs.com/docs/marketing-tools?hsLang=en#main-content) - [Tips and Tricks](https://help.socketlabs.com/docs/marketing-tools?hsLang=en#tips-and-tricks) - [Troubleshooting](https://help.socketlabs.com/docs/troubleshooting?hsLang=en#main-content) - [SocketLabs Inbound SMTP Gateway Errors](https://help.socketlabs.com/docs/troubleshooting?hsLang=en#socketlabs-inbound-smtp-gateway-errors) - [SocketLabs Outbound SMTP Errors](https://help.socketlabs.com/docs/troubleshooting?hsLang=en#socketlabs-outbound-smtp-errors) - [Spotlight Email Analytics](https://help.socketlabs.com/docs/spotlight-email-analytics?hsLang=en) - [Hurricane MTA](https://help.socketlabs.com/docs/hurricane-mta?hsLang=en#main-content) - [Advanced Hurricane Usage](https://help.socketlabs.com/docs/hurricane-mta?hsLang=en#advanced-hurricane-usage) - [Upgrading Hurricane](https://help.socketlabs.com/docs/hurricane-mta?hsLang=en#upgrading-hurricane) - [Troubleshooting](https://help.socketlabs.com/docs/hurricane-mta?hsLang=en#troubleshooting) - [Hurricane Maintenance](https://help.socketlabs.com/docs/hurricane-mta?hsLang=en#hurricane-maintenance) - [Getting Started with Hurricane](https://help.socketlabs.com/docs/hurricane-mta?hsLang=en#getting-started-with-hurricane) - [Basic Hurricane Usage](https://help.socketlabs.com/docs/hurricane-mta?hsLang=en#basic-hurricane-usage) - [Complex Sender](https://help.socketlabs.com/docs/complex-sender?hsLang=en) [![Chill listening crop-3](https://help.socketlabs.com/hs-fs/hubfs/Logos/Logo_Favicon%20-%20large%20-%20cropped.png?width=24&height=24&name=Logo_Favicon%20-%20large%20-%20cropped.png "Chill listening crop-3")](https://www.socketlabs.com) Copyright © 2026, SocketLabs LLC