syn match smDefine "^O[AaBcdDeFfgHiLmNoQqrSsTtuvxXyYzZ]"
syn match smDefine "^O\s"he=e-1
syn match smDefine "^M[a-zA-Z0-9]\+,"he=e-1
syn match smDefine "^T" nextgroup=smTrusted
syn match smDefine "^P" nextgroup=smMesg
syn match smTrusted "\S\+$" contained
syn match smMesg "\S*="he=e-1 contained nextgroup=smPrecedence
syn match smPrecedence "-\=[0-9]\+" contained
" Header Format H?list-of-mailer-flags?name: format
syn match smHeaderSep contained "[?:]"
syn match smHeader "^H\(?[a-zA-Z]\+?\)\=[-a-zA-Z_]\+:" contains=smHeaderSep
" Variables
syn match smVar "\$[a-z\.\|]"
" Rulesets
syn match smRuleset "^S\d*"
" Rewriting Rules
syn match smRewrite "^R" skipwhite nextgroup=smRewriteLhsToken,smRewriteLhsUser
syn match smRewriteLhsUser contained "[^\t$]\+" skipwhite nextgroup=smRewriteLhsToken,smRewriteLhsSep
syn match smRewriteLhsToken contained "\(\$[-*+]\|\$[-=][A-Za-z]\|\$Y\)\+" skipwhite nextgroup=smRewriteLhsUser,smRewriteLhsSep
syn match smRewriteLhsSep contained "\t\+" skipwhite nextgroup=smRewriteRhsToken,smRewriteRhsUser
syn match smRewriteRhsUser contained "[^\t$]\+" skipwhite nextgroup=smRewriteRhsToken,smRewriteRhsSep
syn match smRewriteRhsToken contained "\(\$\d\|\$>\d\|\$#\|\$@\|\$:[-_a-zA-Z]\+\|\$[[\]]\|\$@\|\$:\|\$[A-Za-z]\)\+" skipwhite nextgroup=smRewriteRhsUser,smRewriteRhsSep
syn match smRewriteRhsSep contained "\t\+" skipwhite nextgroup=smRewriteComment,smRewriteRhsSep
syn match smRewriteRhsSep contained "$"
syn match smRewriteComment contained "[^\t$]*$"
" Clauses
syn match smClauseError "\$\."
syn match smElse contained "\$|"
syn match smClauseCont contained "^\t"
syn region smClause matchgroup=Delimiter start="\$?." matchgroup=Delimiter end="\$\." contains=smElse,smClause,smVar,smClauseCont
" Define the default highlighting.
" For version 5.7 and earlier: only when not done already
" For version 5.8 and later: only when an item doesn't have highlighting yet
if version >= 508 || !exists("did_smil_syntax_inits")