We’d need to see the relevant log. Relevant entries from mail.log or the relevant lines from the journal for the postfix unit (run journalctl -fu postfix and then try to send mail while watching…the entries that appear at the moment you try to send are the relevant entries).
Also, if you’re using chroot jails, you need to understand them and the implications of using them. See this thread for a very similar problem which was caused by using chroot jails without equipping the jail with the tools needed to send mail: Can't send mail from WordPress forms