Forwarded emails can act a bit differently than regular emails you received. If you forward an email but it breaks, here's some background information and a workaround.
Many email clients will forward your HTML email and keep the formatting completely intact. However, some programs will break the code used to generate the original email, causing it to appear in the new recipient's inbox as a jumbled mess or raw code. In some cases, it's not even the email client that's breaking the forwarded email, it's the email server. Email servers have been known to break or alter the email's underlying code, which can potentially destroy your email design. Because this happens on the recipient's end, MailChimp can't do anything about this.
If you'd like to allow your subscribers to forward the email that they receive, we strongly recommend that you use our Forward to a Friend merge tag. This merge tag automatically generates a link to the MailChimp-hosted Forward to a Friend form which allows your subscribers to send a link to the archive version of the email.