Constant Edge

Proofpoint's URL Defense rewrites URLs in inbound emails so they can be scanned for threats when clicked. This usually works seamlessly, but it can break inline images or certain links in emails from trusted senders.

You can confirm this is the cause by right-clicking a broken image and checking if the URL starts with urldefense.proofpoint.com. The fix is to add the affected domain(s) to the URL Defense exceptions list.

How to Fix It

1. Log into the Proofpoint Essentials admin dashboard
2. Navigate to Security Settings > Malicious Content > URL Defense
3. Scroll down to the field labelled "Exclude URLs that contain specified domains/IP addresses"
4. Add the affected domain(s), entering each domain on a new line e.g. tickets.example.com
5. Click Save

Tip: Check the broken image URLs to identify the exact domain causing the issue, as it may not be the sender's main domain. For example, a company might send emails from company.com but host images on a separate domain. Add any domains that appear in the broken image URLs.

Note: There are two exclusion fields on this page. "Exclude URLs that contain specified domains" checks each URL individually and only skips rewriting for URLs that match the domain you've added. "Exclude re-writing emails sent by specified senders" skips rewriting on every URL in the entire email from that sender, regardless of where they point.