Stalwart advertises `maxDelayedSend` as a fixed 30 days, but its MTA
rejects any hold beyond `futureRelease`, 7 days by default. Scheduling
a message 8 to 30 days ahead passed the picker and then failed with
"501 5.5.4 Requested hold time exceeds maximum of 604800 seconds".
On Stalwart the advertised 30 days now counts as 7. When a submission
is still rejected for its hold time, the limit from the error message
replaces it for the session, and the composer shows the translated
"later than the server allows" message instead of the raw SMTP reply.
Linus Rath
bab19898d9