Sieve comparators

In addition to the standard Sieve comparators " " and " " described in RFC 5228, and " " described in RFC 4790, the MTA also supports some additional, non-standard comparators.

Because the MTA&#x27;s Sieve implementation supports negative integers in addition to the standard unsigned integers, the MTA supports a " " comparator to compare signed integers.

New in MS 8.0. The MTA&#x27;s comparators " " and " " are similar to the correspondingly named standard comparators, except that all folding white space characters (space, tab, carriage return, line feed) are removed from both the target and pattern strings prior to comparison. Use of these white-space-collapsing comparators is recommended for Sieve comparisons of header values including optional semantically meaningless white space, as many popular email clients exhibit various standards-incompliant behaviors regarding white space in header lines occurring next to MIME encoded-words, or around line folding; standards-compliant Sieve matching may thus not appear to match users&#x27; expectations, when client generation and display of white space diverges  from standards.

New in MS 8.0.1.2. The MTA&#x27;s comparators " " and " " are similar to the correspondingly named standard comparators, except that all folding white space characters (space, tab, carriage return, line feed) are compressed into a single ASCII space and those at the begininng and end of the strings are removed. This is done to both the target and pattern strings prior to comparison. Use of these white-space-compressing comparators is recommended for Sieve comparisons of structured header values that include embedded white space.

See also:
 * Sieve supported extensions