connecting with imap with my iphone takes forever after Upgrade to 26.3.0

I notice in the that the server is very busy and in the /opt/zextra/log/mailbox.log 

I get huge amounts (multiple per seconds) of the following. 

(I changed names and ip-adresses)
 

2026-03-17 11:04:19,768 INFO [ImapServer-0] [name=???????.nl;ip=00.00.00.000;oip=00.00.00.000;via=00.00.00.000(nginx/1.28.0);ua=com.apple.email.maild/3864.400.21;cid=2;] imap - NAMESPACE elapsed=0 (NIO)
2026-03-17 11:04:19,768 INFO [ImapServer-0] [name=???????.nl;ip=00.00.00.000;oip=00.00.00.000;via=00.00.00.000(nginx/1.28.0);ua=com.apple.email.maild/3864.400.21;cid=2;] imap - LIST elapsed=0 (NIO)
2026-03-17 11:04:19,768 INFO [ImapServer-0] [name=???????.nl;ip=00.00.00.000;oip=00.00.00.000;via=00.00.00.000(nginx/1.28.0);ua=com.apple.email.maild/3864.400.21;cid=2;] imap - NAMESPACE elapsed=0 (NIO)
2026-03-17 11:04:19,768 INFO [ImapServer-0] [name=???????.nl;ip=00.00.00.000;oip=00.00.00.000;via=00.00.00.000(nginx/1.28.0);ua=com.apple.email.maild/3864.400.21;cid=2;] imap - LIST elapsed=0 (NIO)
2026-03-17 11:04:19,768 INFO [ImapServer-0] [name=???????.nl;ip=00.00.00.000;oip=00.00.00.000;via=00.00.00.000(nginx/1.28.0);ua=com.apple.email.maild/3864.400.21;cid=2;] imap - NAMESPACE elapsed=0 (NIO)
2026-03-17 11:04:19,768 INFO [ImapServer-0] [name=???????.nl;ip=00.00.00.000;oip=00.00.00.000;via=00.00.00.000(nginx/1.28.0);ua=com.apple.email.maild/3864.400.21;cid=2;] imap - LIST elapsed=0 (NIO)
2026-03-17 11:04:19,768 INFO [ImapServer-0] [name=???????.nl;ip=00.00.00.000;oip=00.00.00.000;via=00.00.00.000(nginx/1.28.0);ua=com.apple.email.maild/3864.400.21;cid=2;] imap - NAMESPACE elapsed=0 (NIO)
2026-03-17 11:04:19,768 INFO [ImapServer-0] [name=???????.nl;ip=00.00.00.000;oip=00.00.00.000;via=00.00.00.000(nginx/1.28.0);ua=com.apple.email.maild/3864.400.21;cid=2;] imap - LIST elapsed=0 (NIO)

@sharif

Can you help me with the above problem. The /opt/zextras/log/mailbox.log is getting huge due to alle the lines and I am afraid it will crash the server because of the file size. (now already 8Gb in several hour)

It seems that due to all the lines (like 10-20 per second) that are written in the logs, the server is getting very slow.

Is it a problem with memcache or a log setting that changed in 26.3.0 ?

@max_s 

It seems like Apple mail's IMAP polling is possibly causing this issue. Also, we need to check what is the Mailbox log level in your server. If it is set to INFO, then you would get massive log, in case of aggressive polling. 

First of all, I would recommend you to use Carbonio Mail app (if you are using any external app to access email)

Now before making any changes or conducting any kind of tests, make sure you have setup a server/file level backup or snapshot.

For temporary relief, we could try truncating the mailbox.log with:

truncate -s 0 /opt/zextras/log/mailbox.log

And you could add this to the cronjob as well.

The default log4j.properties only has time-based rotation (daily). Therefore, an 8GB or even bigger log file within hours will not trigger any rotation until midnight. 

Following workaround should be tested with caution:

#take backup of this file
cp /opt/zextras/conf/log4j.properties.in /opt/zextras/conf/log4j.properties.in.backup


#edit /opt/zextras/conf/log4j.properties.in

# find this line
appender.LOGFILE.filePattern = /opt/zextras/log/mailbox.log.%d{yyyy-MM-dd}

#add .%i at the end as
appender.LOGFILE.filePattern = /opt/zextras/log/mailbox.log.%d{yyyy-MM-dd}.%i

#add following lines after this: appender.LOGFILE.strategy.type = DefaultRolloverStrategy

appender.LOGFILE.policies.size.type = SizeBasedTriggeringPolicy
appender.LOGFILE.policies.size.size = 500MB
appender.LOGFILE.strategy.max = 10

#Add following lines on above this line # spymemcached is too verbose at INFO level.

logger.imap.name = com.zimbra.cs.imap
logger.imap.level = WARN
logger.imap.additivity = false
logger.imap.appenderRef.LOGFILE.ref = mailboxFile

#Apply changes

su - zextras -c "/opt/zextras/libexec/configrewrite mailbox"
systemctl restart carbonio-appserver.target

#in case you are facing issue, revert back the backlup
cp /opt/zextras/conf/log4j.properties.in.backup /opt/zextras/conf/log4j.properties.in
su - zextras -c "/opt/zextras/libexec/configrewrite mailbox"
systemctl restart carbonio-appserver.target

I hope it helps you.

@sharif 

No , still the same problem. I also got a warning and a error

zextras@mail1:~/log$ /opt/zextras/libexec/configrewrite mailbox
OpenJDK 64-Bit Server VM warning: .hotspot_compiler file is present but has been ignored.  Run with -XX:CompileCommandFile=.hotspot_compiler to load the file.

zextras@mail1:~/log$ exit
exit
root@mail1:/opt/zextras/log# systemctl restart carbonio-appserver.target
Failed to restart carbonio-appserver.target: Unit carbonio-appserver.target not found.

@sharif

What I find strange is that opening mail with Webmail or with Outlook (IMAP) is fast Also listing the mails and folders. Only with Iphone I cannot connect anymore and I see all the lines in the logs.

@max_s 

So you are using CE on Ubuntu 22.04LTS?

I would suggest you to use the Carbonio Mail App and compare the performance. 

That's all I could suggest at this point of time.

Ok, i believe it is not a performance issue. Nobody can connect with iphones anymore. Servermessage 'parse error: zero-length content'.

But since this problem occured after the update of Carbonio, is this something Zextras is going to have a look at? Because now we need two different mailcients on our phones since we also have other mailaccounts.

Otherwise can you give me a hint were to look? Do you suggest an Upgrade to Ubuntu 24.04 or something else to solve this problem?

We have exactly the same problem. Essentially, IMAP on iPhones is now unusable. This is unacceptable, and we are urgently waiting for a bug fix. Is there anything in sight?

CE on Ubuntu 24 here, same very sad issue here since the update to 26.3. My boss' iOS 26.3.1 dumped over half a million of those LIST/NAMESPACE requests in a single afternoon, his Apple mail rendered completely useless.

Only thing I can add here is that I can't reproduce this on my dusty old iP7 stuck on iOS 16 so it must be some recent "optimization" incompatibility. When I openssl s_client to :993 I do get proper folder lists when doing LIST "" "*" and NAMESPACE returns "/" and " removed link Guess I'll try to grab a pcap of what nginx proxies to :7143 once he starts spamming the logs again tomorrow...

Posted by: @max_s

↑

Ok, i believe it is not a performance issue. Nobody can connect with iphones anymore. Servermessage 'parse error: zero-length content'.

But since this problem occured after the update of Carbonio, is this something Zextras is going to have a look at? Because now we need two different mailcients on our phones since we also have other mailaccounts.

Otherwise can you give me a hint were to look? Do you suggest an Upgrade to Ubuntu 24.04 or something else to solve this problem?

I wanted to mentioned that I am experiencing the same problem on Red Hat Enterprise Linux 9, after upgrading from CE 25.12.0 to CE 26.3.0 (and later the CE 26.3.1 patch), so this isn't limited to Ubuntu. Virtually all my clients use iOS mail 🙁

Are there instructions to safely downgrade to CE 25.12.0 to get back to a functional environment, or is a patch or server-side workaround being released in the very near future?

Thanks in advance to anyone who can providing an update on this.

Kind regards,

- Richard.

I have the same problem with iphones, fresh install Caronio 26.3.0 on Ubuntu 24.04 LTS.

I have the exact problem. Yesterday I upgraded from previus version, also upgradet Ubuntu on 24.04. Everthing seemd to work great but then I noticed that mail on iPhone dosnt work. I was getting "Servermessage 'parse error: zero-length content'.".

Large portion of people is using iphone mail app for mail so this is unacceptible. Wa forced to revert from snapshot 🙁

@sharif 

I tried Carbonio Mail App just now. Yes it is Fast but not handy when working with multiple mail accounts. I need to logout and then login into different accounts everytime I want to view mail or reply or send a mail. Typing Mailserver en email and password every time I switch mailbox. So Mail app is not an option... unless zextras fixes that issue.

If you have a clue, please give me a hint where to look at regarding the imap problem with Carbonio CE and the Apple Mail app after upgrading to 26.3.0.

Since upgrading to 26.3.0 I am having the same issue, Outlook on Windows/macOS and Carbonio app on iOS work fine, but IMAP from iOS mail does not work!