Mapping operation

All MTA mapping tables are applied in a consistent way. What changes from one mapping to the next is the source of the input strings, and the use of the mapping output strings.

That is, a mapping operation always starts off with an input string and an MTA mapping table. The entries in the mapping table are scanned one at a time from first to last (top to bottom) in the order in which they appear in the table. The left hand side of each entry is used as pattern, and the input string is compared in a case-blind fashion with that pattern. If the comparison of the pattern in a given entry fails, no action is taken; the scan proceeds to the next entry. If the comparison succeeds, (that is, the input probe string "matched" the entry pattern), then the right hand side of the entry is used as a template to produce an output string. The template effectively causes the replacement of the input string with the output string that is constructed from the instructions given by the template.

See also:
 * Mapping tables
 * Mapping entry patterns
 * Mapping entry templates
 * Testing mapping tables