Hello,
We identified a potential regression in Carbonio CE 26 affecting Apple Mail on iPhone after upgrading from Carbonio CE 25.
========================
ENVIRONMENT
========================
- Product: Carbonio CE
- Upgrade: 25 → 26
- Installation: Single server
- Hostname: mail.example.net
- Domain: example.net
========================
CLIENTS
========================
- Affected: Apple Mail (iPhone iOS)
- NOT affected:
- Other Carbonio servers NOT upgraded (same configuration)
- Gmail IMAP
- Webmail
Important:
The same iPhone works perfectly with other Carbonio servers not upgraded to version 26.
========================
SYMPTOMS
========================
- IMAP authentication: OK
- SMTP sending: OK
- Webmail: OK
- Apple Mail connects successfully BUT:
→ mailbox is empty
→ no folders displayed
→ no messages
========================
IMAP MANUAL TEST (OK)
========================
Using openssl:
* OK IMAP4rev1 proxy server ready
a login user@example.net ****
a OK LOGIN completed
a list "" "*"
* LIST (\HasNoChildren) "/" "INBOX"
* LIST (\HasNoChildren) "/" "Sent"
* LIST (\HasNoChildren) "/" "Trash"
a select INBOX
* XXX EXISTS
* OK [UNSEEN XX]
a OK [READ-WRITE] SELECT completed
→ Messages are present and accessible via IMAP
========================
OBSERVED BEHAVIOR (APPLE MAIL)
========================
From mailbox.log:
Apple Mail repeatedly sends:
- NAMESPACE
- LIST
BUT never sends:
- SELECT INBOX
Example log extract:
2026-03-20 10:12:01,123 INFO [ImapSSLServer-10] imap - cmd=LOGIN
2026-03-20 10:12:01,456 INFO [ImapSSLServer-10] imap - cmd=NAMESPACE
2026-03-20 10:12:01,789 INFO [ImapSSLServer-10] imap - cmd=LIST "" "*"
2026-03-20 10:12:02,012 INFO [ImapSSLServer-10] imap - cmd=NAMESPACE
2026-03-20 10:12:02,345 INFO [ImapSSLServer-10] imap - cmd=LIST "" "*"
→ loop without SELECT INBOX
========================
TROUBLESHOOTING DONE
========================
- Mailbox reIndex completed successfully
- Account deleted and recreated → same issue
- Direct IMAP backend (port 7993) tested → same issue
- Standard proxy IMAPS (port 993) restored → same issue
- TLS certificate valid (Let's Encrypt)
- Services status:
- mailbox: running
- proxy: running
- mta: running
- Network (firewall / NAT) ruled out
========================
CONCLUSION
========================
This appears to be an IMAP compatibility issue or regression introduced in Carbonio CE 26 affecting Apple Mail.
The fact that:
- IMAP manual commands work
- Other Carbonio servers (not upgraded) work
- Only Apple Mail is impacted
strongly suggests a protocol or capability-related issue
Conclusion :
Probable bug de compatibilité IMAP introduit dans Carbonio CE 26.
Best regards
Pierre
Our devs are working on this issue. We hope to fix this with a hotfix soon. I do not have a ETA right now. I would update you again by Friday.
Thanks for your understanding.
Regards,
Hello,
Thank you for the update.
We confirm the issue is critical on our side as it impacts all iPhone users.
We will wait for your update and the hotfix.
If needed, we are available to provide logs or perform tests.
Thanks
Bonjour,
Merci pour votre retour.
Nous confirmons que le problème est critique de notre côté car il impacte tous les utilisateurs iPhone.
Nous attendons votre mise à jour et le correctif.
Si besoin, nous pouvons fournir des logs ou effectuer des tests.
Merci
Our devs are working on this issue. We hope to fix this with a hotfix soon. I do not have a ETA right now. I would update you again by Friday.
Thanks for your understanding.
Regards,
Any news ? All and every info would be good since we have lots of users that are disconnected atm. And I need to evaluate wether a full restore of systems back before upgrade is worth the time.
Are there any easier fallbacks?
Hello,
Same situation on our side.
This issue is currently impacting all our iPhone users after the upgrade to Carbonio 26, making IMAP unusable for them (empty mailbox or client stuck).
We understand a hotfix is in progress and we appreciate your work on it.
However, due to the impact in production, we also need to evaluate whether a rollback to the previous version is necessary.
Before taking that decision, could you please let us know:
- if a temporary workaround exists (server-side or configuration)
- or if the hotfix is expected very soon
Any additional information would help us plan accordingly.
Thanks
Bonjour,
Même situation de notre côté.
Ce problème impacte actuellement tous nos utilisateurs iPhone après la mise à jour vers Carbonio 26, rendant l’IMAP inutilisable pour eux (boîte vide ou client bloqué).
Nous comprenons qu’un correctif est en cours et nous apprécions votre travail sur ce sujet.
Cependant, compte tenu de l’impact en production, nous devons également évaluer la possibilité d’un retour arrière vers la version précédente.
Avant de prendre cette décision, pourriez-vous nous indiquer :
- s’il existe un contournement temporaire (côté serveur ou configuration)
- ou si le correctif est attendu très prochainement
Toute information complémentaire nous aiderait à nous organiser.
Merci
I had the same problem after I updated this morning, and only found this thread afterwards. Fortunately, when I looked again in the afternoon, I found more Carbonio updates—and after installing them, it worked again with iOS devices.
Yes the patch seams to have "fixed" some issues however logs are still spamming JAVA errors ... this is every 10 secs for me. for one client at least.
Hello,
Thanks for your feedback, that’s very interesting.
Could you please confirm which exact version you are running now after the additional updates?
Also, did you perform a full upgrade (apt update && apt upgrade) or install a specific Carbonio package?
We are currently experiencing the same issue and would like to confirm if this resolves it before applying updates in production.
Thanks in advance
Bonjour,
Merci pour votre retour, c’est très intéressant.
Pouvez-vous confirmer la version exacte que vous utilisez après les mises à jour supplémentaires ?
Avez-vous effectué une mise à jour complète (apt update && apt upgrade) ou installé un package spécifique Carbonio ?
Nous rencontrons actuellement le même problème et souhaitons confirmer si cela le corrige avant de déployer en production.
Merci d’avance
Hello,
Thank you for the feedback.
This is useful information, because it suggests that the patch may have fixed the main Apple Mail / iPhone IMAP issue, but there still seem to be remaining errors on some FETCH requests.
The warning below looks related to partial content retrieval:
IMAP part requested start out of range
com.zimbra.common.util.StartOutOfBoundsException
So it may indicate that the mailbox can now load again on iOS, but that some messages or MIME parts are still triggering backend exceptions.
On our side, this is important to know before updating:
- has the mailbox loading issue on iPhone been fully resolved?
- are these Java warnings only cosmetic, or do they still cause user-visible problems?
- does this affect only one mailbox / one message, or all iPhone clients?
If possible, it would be very helpful to know:
- the exact package versions installed after the patch
- whether iPhone clients are now usable again in practice
- whether these warnings continue after reconnecting the account
Thanks
Bonjour,
Merci pour ce retour.
C’est une information utile, car cela semble indiquer que le correctif a peut-être résolu le problème principal Apple Mail / IMAP iPhone, mais qu’il reste encore des erreurs sur certaines requêtes FETCH.
L’avertissement ci-dessous semble lié à la récupération partielle du contenu :
IMAP part requested start out of range
com.zimbra.common.util.StartOutOfBoundsException
Cela pourrait donc signifier que la boîte peut désormais se charger sur iOS, mais que certains messages ou certaines parties MIME déclenchent encore des exceptions côté backend.
De notre côté, c’est important à savoir avant de mettre à jour :
- le problème de chargement de la boîte sur iPhone est-il complètement résolu ?
- ces warnings Java sont-ils uniquement cosmétiques, ou provoquent-ils encore des problèmes visibles pour les utilisateurs ?
- cela concerne-t-il uniquement une boîte / un message, ou tous les clients iPhone ?
Si possible, il serait très utile de connaître :
- les versions exactes des paquets installés après le correctif
- si les iPhone sont maintenant réellement utilisables au quotidien
- si ces warnings continuent après reconnexion du compte
Merci
I just updated like guide points to. i.e. apt update , apt upgrade , pending-update, reboot
Running single node on ubuntu 24.
Version 26.3.0
So far I only see this on one of the clients, and it remains while the iphone has the mail app open, but the mail app does not reflect doing anything...
and it seams to work, however I went ahead and removed the mail config on the iphone and currently trying to set it upp again clean, and seeing if this solved this issue. However it seams to give all kinds of error now on setup(i.e. does not goo through, give errors on connection and SSL ( still in progress of investigating that ). ( since other iphone clients work fine it seams )
this did not solve this issue,
i.e. I am still seeing this hammering, even after iphone has synced and all looks ok on the client.
Hello,
Thank you for your detailed feedback.
From what we observe on our side, the situation seems similar:
- after update, IMAP access may appear to work partially
- however iPhone / Apple Mail behavior is still inconsistent
- in some cases, mailbox loads, but in others the client hangs or fails during setup (SSL / connection errors)
We also noticed that the issue can vary between devices, even with the same server configuration.
This suggests that the fix might be partial or still unstable, especially on iOS clients.
Before updating our production environments, we would like to confirm:
- whether a stable and complete fix is available
- whether the current updates are considered safe for production use
Thanks for your feedback
Bonjour,
Merci pour votre retour détaillé.
De notre côté, nous observons une situation similaire :
- après mise à jour, l’accès IMAP semble fonctionner partiellement
- cependant le comportement sur iPhone / Apple Mail reste instable
- dans certains cas la boîte se charge, mais dans d’autres le client bloque ou échoue lors de la configuration (erreurs SSL / connexion)
Nous avons également constaté que le problème peut varier selon les appareils, même avec la même configuration serveur.
Cela semble indiquer que le correctif est partiel ou encore instable, notamment sur les clients iOS.
Avant de mettre à jour nos environnements de production, nous souhaiterions confirmer :
- si un correctif stable et complet est disponible
- si les mises à jour actuelles sont considérées comme sûres pour la production
Merci pour votre retour
this did not solve this issue,
i.e. I am still seeing this hammering, even after iphone has synced and all looks ok on the client.
And to note more, this is not just that one box, I did a grep of the mailbox log and found more users with same problem.
Hello,
Thank you for the confirmation.
This is very important feedback, because it shows that the recent updates do not fully resolve the issue.
From what you describe:
- iPhone sync may now appear to work
- but the server is still continuously generating IMAP backend errors
- so the problem seems only partially fixed
The repeated exception:
com.zimbra.common.util.StartOutOfBoundsException
suggests that some IMAP FETCH / partial content requests are still handled incorrectly.
So at this stage, it seems the current update may improve the visible client behavior in some cases, but the underlying IMAP issue is still present.
For production environments, this is important because:
- user experience may look better
- but the server still logs repeated errors
- and the fix cannot yet be considered clean or complete
We are therefore still waiting for confirmation from the Carbonio team about:
- whether an additional hotfix is planned
- whether these errors are expected to be harmless
- or whether the current patch should still be considered incomplete
Thanks for sharing these logs.
Bonjour,
Merci pour cette confirmation.
C’est une information très importante, car cela montre que les mises à jour récentes ne corrigent pas complètement le problème.
D’après ce que vous décrivez :
- la synchronisation iPhone semble parfois refonctionner
- mais le serveur continue à générer en boucle des erreurs IMAP côté backend
- le problème semble donc seulement partiellement corrigé
L’exception répétée :
com.zimbra.common.util.StartOutOfBoundsException
semble indiquer que certaines requêtes IMAP FETCH / récupération partielle du contenu sont encore mal gérées.
À ce stade, il semble donc que la mise à jour actuelle améliore parfois le comportement visible côté client, mais que le problème IMAP sous-jacent reste présent.
Pour des environnements de production, c’est important car :
- l’expérience utilisateur peut paraître meilleure
- mais le serveur continue à enregistrer des erreurs répétées
- et le correctif ne peut pas encore être considéré comme propre ou complet
Nous restons donc en attente d’une confirmation de l’équipe Carbonio sur :
- l’existence d’un hotfix complémentaire
- le fait que ces erreurs soient sans impact
- ou si le correctif actuel doit encore être considéré comme incomplet
Merci pour le partage de ces logs.