Links Change to mail.domain

Hi all,

On this customer’s site, once in a while, an internal link turns to mail.domain… making it unuseful and delivering a dangerous site message on click (since you change to http instead of https).

When I detected it, I logged in, cleaned cache, run tasks and it was fine, but a few days latter the problem showed up again.

Link is on a Pile - Block and is set using Site Map, so it’s for an /index.php?cID=256 page

What could be causing this?

Thanks in advance

What version of Concrete are you using? And what, if any, add-ons?
Also, what is a “Pile - Block”? Is that a custom block?
Can you provide any screenshots or code (edited for privacy if needed).