email.Utils.parseaddr() does not successfully parse a
field value into a (comment, address) pair if the
address contains a source route with more than one hop.

i.e., it is successfully parses this:

  "God" <@hop1.org:[email protected]>

to get the address <[email protected]>, but it fails to do
the same if supplied with a 2-hop source route:

  "God" <@hop1.org,@hop2.net:[email protected]>

In this case, it gets the comment ("God") right, but
fails to extract the address.

Multi-hop source routes, while deprecated, are still
valid in rfc2822.