I've just installed iRedMail 1.7.4.
I configured amavisd.conf for send to quarantine spam mails.

$final_spam_destiny = D_PASS;
$spam_quarantine_method = 'local:spam.%i.%m.eml';
$spam_quarantine_to = 'spam-quarantine';

I added a value to DB amavisd:
BEFORE

+----+-----------------+--------------------------+
| id | policy_name | spam_quarantine_to |
+----+-----------------+--------------------------+
|  1 | @.                |                                |
+----+-----------------+--------------------------+

AFTER

+----+-----------------+--------------------------+
| id | policy_name | spam_quarantine_to |
+----+-----------------+--------------------------+
|  1 | @.                | spam-quarantine      |
+----+-----------------+--------------------------+

Then I restarted amavisd

The directories structure under $QUARANTINEDIR appeared automatically when the first mailfile was sent to wuarantine, and was created there with de righr filename: spam.20260303T125641.XmFxi-GKloU1, under directory "T".

I made several tests, sending mails with spam simulated (GTUBE), and everything worked right. But after about an hour of inactivity (no more mailfiles were accepted and stored in quarantine directories, and the structure of directories itself disappeared, an did not work anymore.

Y changed in amavisd.conf:

$spam_quarantine_method = 'local:spam.%i.%m.eml';

Restarted amavisd, and it's working again. Why the operation with formatted name of the quarantine worked only temporarily? My preference is to be able to give "format " to filename.