Section 10
Implementations SHOULD take measures to prevent scripts from looping.
Q: Isn't this trivially true because Sieve scripts have no loop
command? Perhaps you meant to say "creating mail loops" instead of
"looping".
Actually, there is separate text about mail loops:
The "redirect" command has considerations regarding loop prevention;
see the command description for recommendations.
I can't remember now why this text is here. Maybe it is just alerting
about buggy implementations that might loop due to buffer overflows, etc.?