[Dovecot] S=xxx missing in new messages

[Andre]

Hi to all!
I’m setting up dovecot 1.2.8 on my system to substitute an older IMAP server and I’m testing all features of Dovecot.

Yesterday I was testing support for zlib, for compressed messages, to set up a new namespace for old mails and I read that it is safe to compress only mails that have the field “S=XXX” in their name (XXX being the original size of message) and to leave uncompressed the ones that don’t have S=XXX in their name.

Testing and searching I discovered that only new mail, mail that used to arrive in mailbox via SMTP have S=XXX, mail copied from another mailbox loose S=XXX. Later I’ve found that this not work anymore, even directly delivered mail messages do not have S=XXX anymore. I use dovecot-lda as delivery program and postfix as SMTP server, but I’ve not touched postfix configuration since one month ago. What can it be? How can I have S=XXX again in my messages file name?

TIA
Andrea