Zimbra fix: A network service error has occurred on Zimbra web client

By default Zimbra uses DoSFilter Throttling Mechanism to avoid large number of request over a short period of time. So if the Zimbra server see requests more than safe amount from an specific IP address / user that will be throttled and the user may face the “A network service error has occurred” error.

This feature is available in 8.5+ to prevent a malicious IP from trying brute force attacks.
For ZCS 8.7 or above

zmprov mcf zimbraHttpThrottleSafeIPs 10.1.1.2/32 zimbraHttpThrottleSafeIPs 192.168.9.0/24

or to append to an existing list of multi-valued zimbraHttpThrottleSafeIPs

zmprov mcf +zimbraHttpThrottleSafeIPs 10.1.1.2/32
zmprov mcf +zimbraHttpThrottleSafeIPs 192.168.9.0/24

For ZCS 8.6, 8.5 or previous

zmprov mcf zimbraHttpThrottleSafeIPs 10.1.1.2 zimbraHttpThrottleSafeIPs 192.168.9.5

or to append to an existing list of multi-valued zimbraHttpThrottleSafeIPs

zmprov mcf +zimbraHttpThrottleSafeIPs 10.1.1.2
zmprov mcf +zimbraHttpThrottleSafeIPs 10.1.1.50
zmprov mcf +zimbraHttpThrottleSafeIPs 192.168.9.5
zmprov mcf +zimbraHttpThrottleSafeIPs 192.168.9.6

Mailbox server restart is required when modifying these attributes.

zmmailboxdctl restart

Check these links below for more parameters on blocking

https://wiki.zimbra.com/wiki/DoSFilter
https://wiki.zimbra.com/wiki/Users_get_%27Network_service_error%27,_and_mailbox.log_shows_%27Access_to_IP_x.x.x.x_suspended,_for_repeated_failed_login%27

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