Increase mail attachment in Zimbra 8.8

Postfix configuration (zimbraMtaMaxMessageSize and message_size_limit)

You can examine the current value of this parameter like this:

# su - zimbra
$ postconf message_size_limit
message_size_limit = 10240000

This configuration parameter is stored in the zimbra ldap directory, and propagated to postconf’s message_size_limit by zmmtaconfig, which is invoked by the zimbra postfix command. The following commands will set the message_size_limit to 2MB (adjust this value to suit your needs):

# su - zimbra
$ zmprov modifyConfig zimbraMtaMaxMessageSize 2048000
$ postfix reload

You can then confirm the changes with this command:

$ postconf | grep message_size_limit

IMAP
Please note: zimbraMtaMaxMessageSize also applies to IMAP APPENDs. The IMAP server will set the largest allowed message size to the zimbraMtaMaxMessageSize value. This would apply to the APPEND operation, which would include actions such as copying a message in an IMAP client.

File upload size configuration (zimbraFileUploadMaxSize)
Until ZCS 5, there is a separate configuration parameter for file uploads . File uploads include, for example, attachments to messages (appointments, tasks, etc), and messages imported by the migration tools (PST Import Wizard, Exchange Migration Wizard, etc). The zimbraFileUploadMaxSize can be configured globally or per server. Note: If you have more than one mailbox node, it may be necessary to restart tomcat on nodes where the commands were not run in order to pick up the changes immediately.

This will globally set the size to 5mb:

# su - zimbra
$ zmprov modifyConfig zimbraFileUploadMaxSize 5000000

Then this will allow 20mb uploads to the server mail2.domain.com:

$ zmprov modifyServer mail2.domain.com zimbraFileUploadMaxSize 20000000

If change does not happen after a short period of time or flushing the cache, you most likely will need to do a full zmcontrol restart on the mailstores. See:

Clarify and update attrs.xml about necessary restarts for mta/file size variableshttp://bugzilla.zimbra.com/show_bug.cgi?id=80002
The size of the zimbraMailContentMaxSize controls the overall message size

su - zimbra
zmprov ms `zmhostname` zimbraMailContentMaxSize 20000000 
zmprov modifyConfig zimbraMailContentMaxSize 20000000

<attr id=”807″ name=”zimbraMailContentMaxSize” type=”long” cardinality=”single” optionalIn=”globalConfig,server” flags=”serverInherited” since=”6.0.0_BETA1″>
<globalConfigValue>10240000</globalConfigValue>
<desc>Maximum size in bytes for the <content > element in SOAP. Mail content larger than this limit will be truncated.</desc>
</attr>

Here is an example to set the max message size to 42MB

zmprov ms `zmhostname` zimbraFileUploadMaxSize 44040192
zmprov ms `zmhostname` zimbraMailContentMaxSize 44040192
zmprov mcf zimbraMtaMaxMessageSize 44040192
postfix reload

one thing to watch for is to use a conversion toll to calculate the value in bytes otherwise it won’t be accepted

If change does not happen after a short period of time or flushing the cache, you most likely will need to do a full zmcontrol restart on the mailstores. See:

Clarify and update attrs.xml about necessary restarts for mta/file size variableshttp://bugzilla.zimbra.com/show_bug.cgi?id=80002

Src: https://wiki.zimbra.com/wiki/Configuring_maxmessagesize