Zimbra Mail Error: not enough free space in mail queue

While you are sending mails zimbra server and getting Error Message as “not enough free space in mail queue” under /var/log/zimbra.log Then you should try out this solution.

Step 1. Login into the server, and then login as zimbra as follows:

Step 2. verify the Postfix message_size_limit, by default it should be 10MB (i.e. ‘10240000’ bytes) as follows:

Step 3. If the value is higher than that, set it as follows to 10MB

Now try sending Mail, It should work.