Stalwart currently advertises a hard coded maxDelayedSend value of 2592000 seconds (30 days), while the SMTP FutureRelease limit is configurable through MTA extension settings.
This causes JMAP clients such as iHasMail, Bulwark, or JMAP-Webmail to limit scheduled sending to 30 days even when the administrator has configured SMTP FutureRelease for a longer duration.
It would be useful for JMAP maxDelayedSend to either be independently configurable or use the same value from SMTP FutureRelease.
This would keep the advertised JMAP capability consistent with the server’s configured delayed-delivery policy.
This hard coded value appears to have been unchanged since the initial implementation about 2 years ago: Settings hot reloading - Part 2 · stalwartlabs/stalwart@5756815 · GitHub