Thanks for writing mblaze!

Here is a small bug: When replying to a message containing

 Message-Id: <dddddddddddddddddddddddddddddddddd@d>
 References: <aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa@a> <bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb@b> <ccccccccccccccccccccccccccccccc@c>

mrep(1) on FreeBSD 11 produces

 References:
  =?UTF-8?Q?_<aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa@a>n<bbbbbbbbbbbbbbbbbbbbbb?=
  =?UTF-8?Q?bbbbbbbbbbbbbbb@b>n<ccccccccccccccccccccccccccccccc@c>?=
  <dddddddddddddddddddddddddddddddddd@d>

Here's a patch: