While working with Zimbra, I figured out today that I needed to increase the attachment size limit of the message to send larger messages. The default attachment size limit is 10MB. Even if the attachment is a little less than 10MB, it won’t send quoting the same error that the maximum message size is crossing the limits. This is because of the fact that Zimbra will encode the message into base-64 encoding. With base64-encoding, the message size becomes larger than 10MB. So here is the command I used to increase the limit from 10MB to 20MB.
login:root
password:*****
[root@mail ~]# su zimbra
[zimbra@mail root]$ zmprov mcf zimbraMtaMaxMessageSize 20480000
20480000 is the message size in bytes. No need to restart Zimbra Server .. now you can send messages up to 20MB.
Note: Usually it is not advisable to increase the size of message to very large quantities as it will slow down the server performance.
Technorati Tags: zimbra, attachment, message size limit,
Filed under: Uncategorized | Tagged: Linux, systems administration, troubleshooting, Zimbra

thanks!
this really helped me.
Thanks,
that was cool, and very helpful