To make sure RFC2919 is not violated.
"<" and ">" will be added if no list description exists.
The maxlinelen=998 is a precaution to keep the may line
length of RFC2822.
Fixes [ 880073 ] list-id might violate RFC2919 and RFC2822
https://sourceforge.net/tracker/index.php?func=detail&aid=880073&group_id=103&atid=100103
patch for mailman 2.1.4 to make better list-ids
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user_id=67709
This was already fixed in CVS/2.1.6b.