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Custom Envelope Sender

Custom Envelope Sender

By default, when sending an email to a target, the message will be sent from the supporter’s email address.

This can be problematic for email deliverability, especially with the advance of DMARC, since certain providers restrict delivery using this method. To improve delivery, you can enable a custom envelope which will modify the sender’s email address with a new domain that is authenticated.

The “Reply to” email address is still the supporter’s own, so any targets replying would still be replying to the supporter and not the modified address.

This feature provides a way around the need to ‘spoof’ a supporter’s email address when sending from our servers, and is the recommended option to ensure optimal deliverability.

When using this, what will it look like?

The target will receive the email from the supporter, using their first and last names as their display name, and using their names along with the envelope domain for the From email address.

For example, say supporter Elvis Presley ( used the campaign to email a custom target, with an envelope of The target would receive the email from, but if they replied it would go to the “real” email address of

If the First and Last Name fields are not completed, then the target will receive an email from

How do I set this up?

1) Set up a sending domain

You need to have a domain ready that will be used as the supporter’s sending email address’s domain, for example This can be a subdomain of your own site, or a brand new domain, but shouldn’t be something you are using already. You will need to set this up yourselves. Subdomains can usually be added as part of your domain package. Talk to your IT team if you need help.

2) Add domain authentication to the domain

You then need to have SPF, DKIM and Return Path on this domain set up and working. Instructions and verification of this will be shown when first adding the envelope domain to your email-to-target page. To see this, go to the Admin page of your email-to-target page, click on the Sender Settings tab, add a new sender for your domain and verify. 

Alternatively, the instructions are shown below. 

Domain authentication instructions

Replace every instance of the example domain “” with your own domain.

SPF: add or update the TXT record for to include

DKIM: create the two following CNAME records for Custom Domain Authentication with the value (include the final full stop) with the value (include the final full stop)

Return path: create the following CNAME to align return path processing: with the value (include the final full stop)

3) Enable the custom envelope sender for your page

Continue reading to do this next step.

Enabling a Custom Envelope Sender in a campaign

Once you have completed the previous steps, the ‘Custom Envelope Sender’ settings can be accessed under ‘Sender Settings’ within the ‘Admin’ section of your email to target page.

If you have not used this feature before, there won’t be any custom envelope senders in your account yet. Click on the ‘Manage Senders’ button to add new sender envelopes to your account:

A new sender is added by clicking New Domain:

It is recommended that you do not use a domain that is used in general email broadcasts. For example, if the primary domain for email is, using will help protect email delivery on

In order to make sure that the domain is set up correctly for email deliverability, we perform a series of steps to validate that the domain is suitable for use as a custom envelope sender domain (see here for more regarding your domain authentication). If all the validation steps are successful, you will be able ‘Complete’ the setup. The custom envelope sender is now ready to be selected.

In this example, we’re using the domain ‘’ as the custom sender domain (please do not use this yourselves!).

This means that to recipients, any emails sent to a target contact will appear to come from a If the target wishes to reply via email, and simply hits ‘Reply’ in their email client, the Reply-To address will use the actual supporter’s email address and the recipient will still be able to respond directly to the supporter.

Your supporters will not need to do anything differently and won’t even notice that this has been enabled. Responses via email will still be sent to their regular email address, but they may have a lot better chance of getting through to the intended target with their message.


A target has replied saying their responses are bouncing, what now? We recommend setting a catch-all forwarding rule for your ETT custom envelope domain to a mailbox you control, so you can receive any emails that targets may be attempting to send. While it’s true that the ‘Reply-to:’ address used in ETT headers will still be the original email address of your supporter, the ‘From:’ address will be their name followed by your domain, so something like: [email protected] Some targets may attempt to reply to this address rather than the designated ‘Reply-To:’ address, so setting a catch-call forwarding rule for your ETT domain to a managed mailbox will allow you to effectively direct that mail.



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