Zimbra 8.0.4 - 451 4.7.1 service unavailable

[X_Ch4n]

Hi all,

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
Please help....
Thanks to all.

[gren]

This may be related to https://bugzilla.zimbra.com/show_bug.cgi?id=93569 Investigating that suggests that increasing milter_max_idle_time may help. (We tried 300)