Outlook is very archaic with the way it handles email code. Unfortunately this is not something that Zenu has control over. When an email is forwarded from Outlook, the mail client strips out much of the code that styles the email. This can cause buttons to be misaligned and other formatting to be lost.
At Zenu we do our best to ensure communication sent from our system to multiple platforms looks its best. Unfortunately in the case of Outlook when an email is forwarded by the recipient or replied we have no control over what happens to the email.
Please see the link below for compatibility for CSS support in HTML emails- in other words, which mail applications and programs are the most compatible in regards to HTML.