We have a saved Message Template for logins to our system that we send out frequently, we have noticed that when we paste in the username to the template within the body of the email it is changing the link behind it to an old customers email address. Any ideas why this might be happening or how we can stop it..

We paste in the new customer email address on the line Your Username is .. (eg email@email.co.uk) it shows the correct email address but on sending, it is changing the mailto link behind it to another email address beginning with info@.
So when the end user then copies the email their side if tells them the credentials are wrong because it copies the info@ email address.
Any suggestions gratefully received.