i'm a new zimbra user, so i don't know much about it.
When my external users try to send an email with 3mb more attachements, they got this error "451 4.7.1 service unavailable". They can't to send to an external domain and same domain too. They can send only using the webmail interface with any attacchements 10mb or more)
I googled and found this solution, but it doesn't work for me.
This is the output of "zmlocalconfig | grep milter" command:
zmlocalconfig | grep milter
milter_bind_port = 0
milter_command_timeout = 60
milter_connect_timeout = 60
milter_content_timeout = 300
milter_in_process_mode = false
milter_max_idle_time = 120
milter_thread_keep_alive_time = 120
milter_write_chunk_size = 1024
milter_write_timeout = 120
Thanks to all.