Is your users source of type SQL or LDAP?

We use MySQL as db

Share you DB schema.

We use following schema for the mailbox table.

CREATE TABLE `mailbox` (
  `username` varchar(255) NOT NULL,
  `password` varchar(255) NOT NULL,
  `name` varchar(255) DEFAULT NULL,
  `quota` bigint(20) NOT NULL DEFAULT 102400,
  `local_part` varchar(255) NOT NULL,
  `domain` varchar(255) NOT NULL,
  `kind` varchar(100) NOT NULL DEFAULT '',
  `multiple_bookings` int(11) NOT NULL DEFAULT -1,
  `created` datetime NOT NULL DEFAULT current_timestamp(),
  `modified` datetime DEFAULT NULL ON UPDATE current_timestamp(),
  `active` tinyint(1) NOT NULL DEFAULT 1,
  `attributes` longtext CHARACTER SET utf8mb4 COLLATE utf8mb4_bin DEFAULT NULL CHECK (json_valid(`attributes`)),
  `mailbox_path_prefix` varchar(150) DEFAULT '/var/vmail/',
  `description` varchar(255) DEFAULT NULL,
  PRIMARY KEY (`username`),
  KEY `domain` (`domain`),
  KEY `kind` (`kind`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 ROW_FORMAT=DYNAMIC

password is hashed with BLF-CRYPT

You'll need to drop your session table (OCSSessionsFolderURL) and restart sogod.