Restrictions on default.sieve

Are there actions that default.sieve cannot take?

I tried adding

redirect :copy "backup+foo@local.example.com"

and… nothing.

No errors I can find, but also no mail being redirected.

I also tried

# there must be 'from' in the received headers if header :contains "received" "from" { redirect :copy "backup+foo@local.example.com" }

And

if header :index 1 :contains "received" "from" { redirect :copy "backup+foo@local.example.com" }

But still, no mail in .foo for the backup user (yes, dovecot is setup to autofile +address into mailboxes, and that works).

-- You couldn't say, 'I had orders.' You couldn't say, 'It's not fair.' No one was listening. There were no Words. You owned yourself. ... Not Thou Shalt Not. Say I Will Not. --Feet of Clay