The verification email for CSO contains dodgy line endings, and looks like this in Mutt:
Thanks for registering with Stack Overflow Careers^M ^M To ensure that potential employers can reach you via email, we need to confirm your email address. All it takes is a single click.^M
The whole message shows a ^M at the end of each line. The encoded form of the text/plain message looks like:
Content-Transfer-Encoding: quoted-printable Thanks for registering with Stack Overflow Careers=0D =0A=0D=0ATo ensure= that potential employers can reach you via email, we need to confirm your= email address. All it takes is a single click.=0D =0A=0D=0AClick here to=
I'm pretty sure there isn't supposed to be that extra
=0D in there (especially not with that extra space), and taking it out allows the message to render correctly in Mutt.