dovecot/Pigeonhole sieve sets seen flag

Hi,

I'm using dovecot, running Ubuntu 24.04 with dovecot 1:2.3.21+dfsg1-2ubuntu6  and postfix. Since Ubuntu dropped mailfilter for 24.04, I am replacing mailfilter with the sieve filter.

Problem/Question:

I am using something like

if header :matches "Subject" "htest" { addflag "$label1"; fileinto :create "Test.${year}.${month}"; stop; }

following https://doc.dovecot.org/2.3/configuration_manual/sieve/examples/

which works, but not as expected: When having the addflag, the mail is delivered as seen, i.e. put in the /cur directory of the Maildir folder. Without the addflag, it is put into /new , where it belongs to (as unseen).

Why does    addflag "$label1";  mark the Mail as seen?

regards

Hadmut (please respond directly, I am not on this list)