Processing of rules requires that all addresses be divided into
tokens. The -d22.1 (a.k.a.
-d22) debugging switch causes
sendmail to print the various steps it takes in
tokenizing an address.
In addition to tokenizing, the prescan( )
routine also normalizes addresses. That is, it removes RFC2822-style
comments and recognizes quoted strings. Be aware that rules are also
viewed as addresses and processed by prescan( )
when the configuration file is being read.
The -d22.1 debugging switch tells
sendmail to complain if the first token in the
address it is parsing turns out to be nothing:
prescan: null leading token
This can happen if an address (or rule) contains only RFC2822-style
comments in parentheses.