As was mentioned, rules exist to rewrite addresses. We won’t cover the reasons this rewriting needs to be done just yet, but we will concentrate on the general behavior of rewriting.
Before any rules are called to perform rewriting, a temporary buffer called the “workspace” is created. The address to be rewritten is then tokenized and placed into that workspace. The process of tokenizing addresses in the workspace is exactly the same as the tokenizing of rules that you saw before:
email@example.com becomes→ gw @ wash . dc . gov
Here, the tokenizing characters defined by the
OperatorChars option (OperatorChars) and those defined internally by
sendmail caused the address to be broken into
seven tokens. The process of rewriting changes the tokens in the
← workspace is "gw" "@" "wash" "." "dc" "." "gov" R lhs rhs R lhs rhs ← rules rewrite the workspace R lhs rhs ←workspace is "gw" "." "LOCAL"
Here, the workspace began with seven tokens. The three hypothetical rules recognized that this was a local address (in token form) and rewrote it so that it became three tokens.