==== REQUIRED BASIC INFO OF YOUR IREDMAIL SERVER ====
- iRedMail version (check /etc/iredmail-release): 1.6.4 MARIADB edition.
- Deployed with iRedMail Easy or the downloadable installer? Download
- Linux/BSD distribution name and version: Rocky 9.2
- Store mail accounts in which backend (LDAP/MySQL/PGSQL): MySQL
- Web server (Apache or Nginx): Nginx
- Manage mail accounts with iRedAdmin-Pro? No
- [IMPORTANT] Related original log or error message is required if you're experiencing an issue.
====

Installed few days ago.
Added some accounts for testing. No problems with IMAP/SMTP.
Two day ago I added a user thatt need to share an Outlook Calendard with his mobile iPhone (iOS 17).
Configured Outlook (365), to access mail via IMAP. Calendar via Outlook CalDav Synchronizer.
Imported the calendars via Outlook (350+150 MB too big for importing from Sogo Web interface).
Configured Apple Mail into the iPhone (Exchange server). All seems work fine.
Today the user claims that mail doesn't sinc last messagges in the Phone.
Also Problems with the Calendar and mail in subfolder not present.
Tried to install Outlook for iOS. Same (worse), situation.
I tried to configure the account into an Outlook 2016 (Exchange Active Sync protocol), and same issues.
Web SOGo interfaces works fine.
I noticied that sogo packages was updated more times from this version that was installed 2 days ago:

2023-09-18T13:00:44+0200 SUBDEBUG Upgrade: sope49-xml-4.9-20230918_1664.el9.2.1.x86_64
2023-09-18T13:00:44+0200 SUBDEBUG Upgrade: sope49-core-4.9-20230918_1664.el9.2.1.x86_64
2023-09-18T13:00:45+0200 SUBDEBUG Upgrade: sope49-gdl1-4.9-20230918_1664.el9.2.1.x86_64
2023-09-18T13:00:45+0200 SUBDEBUG Upgrade: sope49-gdl1-contentstore-5.8.4.20230918-1.el9.x86_64
2023-09-18T13:00:45+0200 SUBDEBUG Upgrade: sope49-ldap-4.9-20230918_1664.el9.2.1.x86_64
2023-09-18T13:00:45+0200 SUBDEBUG Upgrade: sope49-mime-4.9-20230918_1664.el9.2.1.x86_64
2023-09-18T13:00:45+0200 SUBDEBUG Upgrade: sope49-appserver-4.9-20230918_1664.el9.2.1.x86_64
2023-09-18T13:00:45+0200 SUBDEBUG Upgrade: sope49-sbjson-2.3.1-20230918_1664.el9.2.1.x86_64
2023-09-18T13:00:45+0200 SUBDEBUG Upgrade: sope49-cards-5.8.4.20230918-1.el9.x86_64
2023-09-18T13:00:46+0200 SUBDEBUG Upgrade: sogo-5.8.4.20230918-1.el9.x86_64
2023-09-18T13:01:18+0200 SUBDEBUG Upgrade: sogo-activesync-5.8.4.20230918-1.el9.x86_64
2023-09-18T13:01:18+0200 SUBDEBUG Upgrade: sogo-tool-5.8.4.20230918-1.el9.x86_64
2023-09-18T13:01:18+0200 SUBDEBUG Upgrade: sope49-gdl1-mysql-4.9-20230918_1664.el9.2.1.x86_64
2023-09-18T13:01:18+0200 SUBDEBUG Upgrade: sogo-ealarms-notify-5.8.4.20230918-1.el9.x86_64
2023-09-20T11:59:08+0200 SUBDEBUG Upgrade: sope49-xml-4.9-20230920_1664.el9.2.1.x86_64
2023-09-20T11:59:08+0200 SUBDEBUG Upgrade: sope49-core-4.9-20230920_1664.el9.2.1.x86_64
2023-09-20T11:59:09+0200 SUBDEBUG Upgrade: sope49-gdl1-4.9-20230920_1664.el9.2.1.x86_64
2023-09-20T11:59:09+0200 SUBDEBUG Upgrade: sope49-gdl1-contentstore-5.8.4.20230920-1.el9.x86_64
2023-09-20T11:59:09+0200 SUBDEBUG Upgrade: sope49-ldap-4.9-20230920_1664.el9.2.1.x86_64
2023-09-20T11:59:09+0200 SUBDEBUG Upgrade: sope49-mime-4.9-20230920_1664.el9.2.1.x86_64
2023-09-20T11:59:09+0200 SUBDEBUG Upgrade: sope49-appserver-4.9-20230920_1664.el9.2.1.x86_64
2023-09-20T11:59:09+0200 SUBDEBUG Upgrade: sope49-sbjson-2.3.1-20230920_1664.el9.2.1.x86_64
2023-09-20T11:59:09+0200 SUBDEBUG Upgrade: sope49-cards-5.8.4.20230920-1.el9.x86_64
2023-09-20T11:59:09+0200 SUBDEBUG Upgrade: sogo-5.8.4.20230920-1.el9.x86_64
2023-09-20T11:59:28+0200 SUBDEBUG Upgrade: sogo-activesync-5.8.4.20230920-1.el9.x86_64
2023-09-20T11:59:28+0200 SUBDEBUG Upgrade: sogo-tool-5.8.4.20230920-1.el9.x86_64
2023-09-20T11:59:28+0200 SUBDEBUG Upgrade: sope49-gdl1-mysql-4.9-20230920_1664.el9.2.1.x86_64
2023-09-20T11:59:28+0200 SUBDEBUG Upgrade: sogo-ealarms-notify-5.8.4.20230920-1.el9.x86_64
2023-09-21T17:19:35+0200 SUBDEBUG Upgrade: sope49-xml-4.9-20230921_1664.el9.2.1.x86_64
2023-09-21T17:19:35+0200 SUBDEBUG Upgrade: sope49-core-4.9-20230921_1664.el9.2.1.x86_64
2023-09-21T17:19:35+0200 SUBDEBUG Upgrade: sope49-gdl1-4.9-20230921_1664.el9.2.1.x86_64
2023-09-21T17:19:35+0200 SUBDEBUG Upgrade: sope49-gdl1-contentstore-5.8.4.20230921-1.el9.x86_64
2023-09-21T17:19:35+0200 SUBDEBUG Upgrade: sope49-ldap-4.9-20230921_1664.el9.2.1.x86_64
2023-09-21T17:19:35+0200 SUBDEBUG Upgrade: sope49-mime-4.9-20230921_1664.el9.2.1.x86_64
2023-09-21T17:19:35+0200 SUBDEBUG Upgrade: sope49-appserver-4.9-20230921_1664.el9.2.1.x86_64
2023-09-21T17:19:35+0200 SUBDEBUG Upgrade: sope49-sbjson-2.3.1-20230921_1664.el9.2.1.x86_64
2023-09-21T17:19:35+0200 SUBDEBUG Upgrade: sope49-cards-5.8.4.20230921-1.el9.x86_64
2023-09-21T17:19:35+0200 SUBDEBUG Upgrade: sogo-5.8.4.20230921-1.el9.x86_64
2023-09-21T17:20:04+0200 SUBDEBUG Upgrade: sogo-activesync-5.8.4.20230921-1.el9.x86_64
2023-09-21T17:20:05+0200 SUBDEBUG Upgrade: sogo-tool-5.8.4.20230921-1.el9.x86_64
2023-09-21T17:20:05+0200 SUBDEBUG Upgrade: sope49-gdl1-mysql-4.9-20230921_1664.el9.2.1.x86_64
2023-09-21T17:20:05+0200 SUBDEBUG Upgrade: sogo-ealarms-notify-5.8.4.20230921-1.el9.x86_64

I don't know if the problems are related to the updates, but I can't find other correlations.
Activated debug mode in SOGo (SOGoEASDebugEnabled = YES;).
It produces tons of info that I am not able to fully understand.
I some rows:

Sep 21 18:41:41 sogod [7004]: <0x0x5609e06146b0[NGImap4Client]> TLS started successfully.
Sep 21 18:41:41 sogod [7004]: <0x0x5609e06146b0[NGImap4Client]> Note: no key found for sorting, using 'DATE': (null)
Sep 21 18:41:41 sogod [7004]: <0x0x5609e0960030[SOGoActiveSyncDispatcher]> EAS - sortedBySequence (2312) - lastObject: 2317-2457
Sep 21 18:41:41 sogod [7004]: <0x0x5609e0960030[SOGoActiveSyncDispatcher]> EAS - allCacheObjects (36) - lastObject: 2352-2539
Sep 21 18:41:41 sogod [7004]: <0x0x5609e0960030[SOGoActiveSyncDispatcher]> EAS - found in cache: 1  k = 1
Sep 21 18:41:41 sogod [7004]: <0x0x5609e0960030[SOGoActiveSyncDispatcher]> EAS - Dealing with cacheObject: 2318-2458
Sep 21 18:41:41 sogod [7004]: <0x0x5609e0960030[SOGoActiveSyncDispatcher]> EAS - ADD!
Sep 21 18:41:41 sogod [7004]: <0x0x5609e0960030[SOGoActiveSyncDispatcher]> EAS - first uid added 2318
Sep 21 18:41:41 sogod [7004]: <0x0x5609e0960030[SOGoActiveSyncDispatcher]> EAS - Dealing with cacheObject: 2319-2459
Sep 21 18:41:41 sogod [7004]: <0x0x5609e0960030[SOGoActiveSyncDispatcher]> EAS - ADD!
Sep 21 18:41:41 sogod [7004]: <0x0x5609e0960030[SOGoActiveSyncDispatcher]> EAS - Dealing with cacheObject: 2320-2465
Sep 21 18:41:41 sogod [7004]: <0x0x5609e0960030[SOGoActiveSyncDispatcher]> EAS - ADD!
Sep 21 18:41:41 sogod [7004]: <0x0x5609e0960030[SOGoActiveSyncDispatcher]> EAS - Dealing with cacheObject: 2322-2466
Sep 21 18:41:41 sogod [7004]: <0x0x5609e0960030[SOGoActiveSyncDispatcher]> EAS - ADD!
Sep 21 18:41:41 sogod [7004]: <0x0x5609e0960030[SOGoActiveSyncDispatcher]> EAS - Dealing with cacheObject: 2324-2470
Sep 21 18:41:41 sogod [7004]: <0x0x5609e0960030[SOGoActiveSyncDispatcher]> EAS - ADD!
Sep 21 18:41:41 sogod [7004]: <0x0x5609e0960030[SOGoActiveSyncDispatcher]> EAS - Dealing with cacheObject: 2325-2473
Sep 21 18:41:41 sogod [7004]: <0x0x5609e0960030[SOGoActiveSyncDispatcher]> EAS - ADD!
Sep 21 18:41:41 sogod [7004]: <0x0x5609e0960030[SOGoActiveSyncDispatcher]> EAS - Dealing with cacheObject: 2326-2475
Sep 21 18:41:41 sogod [7004]: <0x0x5609e0960030[SOGoActiveSyncDispatcher]> EAS - ADD!
Sep 21 18:41:41 sogod [7004]: <0x0x5609e0960030[SOGoActiveSyncDispatcher]> EAS - Dealing with cacheObject: 2323-2476
Sep 21 18:41:41 sogod [7004]: <0x0x5609e0960030[SOGoActiveSyncDispatcher]> EAS - ADD!
Sep 21 18:41:41 sogod [7004]: <0x0x5609e0960030[SOGoActiveSyncDispatcher]> EAS - Dealing with cacheObject: 2327-2478
Sep 21 18:41:41 sogod [7004]: <0x0x5609e0960030[SOGoActiveSyncDispatcher]> EAS - ADD!
Sep 21 18:41:41 sogod [7004]: <0x0x5609e0960030[SOGoActiveSyncDispatcher]> EAS - Dealing with cacheObject: 2328-2480
Sep 21 18:41:41 sogod [7004]: <0x0x5609e0960030[SOGoActiveSyncDispatcher]> EAS - ADD!
Sep 21 18:41:41 sogod [7004]: <0x0x5609e0960030[SOGoActiveSyncDispatcher]> EAS - Dealing with cacheObject: 2329-2483
Sep 21 18:41:41 sogod [7004]: <0x0x5609e0960030[SOGoActiveSyncDispatcher]> EAS - ADD!
Sep 21 18:41:41 sogod [7004]: <0x0x5609e0960030[SOGoActiveSyncDispatcher]> EAS - Dealing with cacheObject: 2331-2485
Sep 21 18:41:41 sogod [7004]: <0x0x5609e0960030[SOGoActiveSyncDispatcher]> EAS - ADD!
/usr/sbin/sogod: symbol lookup error: /usr/lib64/GNUstep/SOGo/Mailer.SOGo/Mailer: undefined symbol: TNEFCheckForSignature
Sep 21 18:41:41 sogod [6708]: <0x0x5609e08f8800[WOWatchDogChild]> child 7004 exited with code 127
Sep 21 18:41:41 sogod [6708]: <0x0x5609e08f8800[WOWatchDogChild]> avoiding to respawn child before 2023-09-21 18:41:42 +0200