I received an email from Twitter with a warning injected in the email "MailShark Corporation has detected definite fraud in the website at "t.co". Do not trust this website:"
Is this from the MailShark service and is this because of the t.co redirect?
Yes and yes. By default we have URI detection mechanisms in
place to detect if there is a difference between the "displayed" URL and the "embedded" URL in HTML messages. If there is a
difference, MailShark will alert of the difference via a warning in red text prior to the questionable link.
Various other checks are performed using the same technique like
detecting a 1x1 pixel image referencing a URL - invisible to the naked eye but something spammers use to know you
are viewing their email and verify the recipient address and adding you to more spam lists.
If you'd like us to add a rule to not "display" these in your twitter emails please advise. We can do this for all email from *@twitter.com or other domains, or for all inbound domains.
Disinfection of questionable URLs will still occur so protection is not reduced in any way, just warnings won't be seen in the emails.