You may face the issue when the HTML versions of your emails are not being delivered while the text versions of the emails are delivered. Your email server administrator found out that server sending HTML versions was blacklisted while the text versions are sent from another non-blacklisted server.
You can check that server is blacklisted by the Barracuda security center:
Most probably Barracuda security center is blocking server IP because of its poor sending reputation. Please raise a support ticket and provide a blacklisted server IP address(es) (ask your email server administrator to check and provide you all blacklisted IP addresses used to send emails through Lyris HQ).
Lyris HQ support will send the unblock request to Barracuda, but the server can be blacklisted again if you won't configure domain customizations recommended by Lyris HQ.
Please read and follow these best practices to increase your IP address reputation:
- Configure DKIM for all sender domains.
- Configure a Custom Return Path (CRP).
- Mask reply-to addresses.
- Customize "From Address" for Mailings.
Also, make sure to follow common email marketing best practices:
- Don’t purchase email lists
- Don’t use list harvesting techniques such as web scraping or spambots
- Use opt-in or confirmed opt-in permission methods for all new subscribers
- Consistently use list hygiene best practices
- Make sure your email program complies with CAN-SPAM Act requirements
To remove a farm listed on Barracuda's Intent BlackList request removal via email to email@example.com (alternatively use the Removal Request form).
Share with the customer the answer from Barracuda, and notify the customer that he\she should follow practices mentioned above to avoid blacklisting in the future.
After Barracuda will unblock IP address your HTML versions of the emails will start being delivered.