Test: DNS Prefetch - Link

In the <body> of the HTML part, place a tag as follows: <link rel="dns-prefetch" href="http://TRACKING_URL/"> Some email clients and web browsers perform DNS pre-fetching on URLs in Anchor tags of emails. This test wont leak your IP address, but it will leak the IP address of your DNS resolvers, which can provide information on which ISP you're using and potentially your general location. Some mail servers do DNS lookups on these URLs as part of their spam filtering process, so you may see the IP address of the mail servers DNS resolvers here, as well as, or instead of, your own.