Zimbra: A network service error has occurred

Lately from time to time on one of my Zimbra servers I was getting A network service error has occurred error message. Restarting the Zimbra service was fixing the issue but it was time to find out why this is happening.

This is the the screen I’m getting and nothing in my log files:

Zimbra Network Service Error

Now my problem was that I’m using a nginx proxy to route the traffic to my server and I changed the proxy server IP address and forgot about the Zimbra DosFilter Throttling Mechanism

The denial-of-service filter or DoSFilter was added to the mailbox server in ZCS 8.0 to throttle clients sending a large number of requests over a very short period of time. The DoSFilter is applied to all requests for service, mailbox and admin.

My solution was to add my nginx ip to zimbraHttpThrottleSafeIPs

For Zimbra Servers 8.7 and above you need to add CIDR address

zmprov mcf zimbraHttpThrottleSafeIPs 10.1.2.3/32 zimbraHttpThrottleSafeIPs 192.168.4.0/24

or append

zmprov mcf +zimbraHttpThrottleSafeIPs 10.1.2.3/32
zmprov mcf +zimbraHttpThrottleSafeIPs 192.168.4.0/24

For Zimbra Servers 8.6, 8.5 and previous you need to add each IP

zmprov mcf zimbraHttpThrottleSafeIPs 10.1.2.3 zimbraHttpThrottleSafeIPs 192.168.4.5

or append

zmprov mcf +zimbraHttpThrottleSafeIPs 10.1.2.3
zmprov mcf +zimbraHttpThrottleSafeIPs 10.1.2.50
zmprov mcf +zimbraHttpThrottleSafeIPs 192.168.4.5
zmprov mcf +zimbraHttpThrottleSafeIPs 192.168.4.6

Finally you need to restart the Zimbra Mailbox server

zmmailboxdctl restart

You are now done and should not have this issue anymore.


Additionally you can also adjust the DosFilter parameters

zmprov mcf zimbraHttpDosFilterDelayMillis 20
zmprov mcf zimbraHttpDosFilterMaxRequestsPerSec 100

Also from 8.5 and above you can Block IPs on Repeated Failed Login

Set the DoS filter to block an IP after 5 failed login attempts for 25 minutes, you would do this:

zmprov mcf zimbraInvalidLoginFilterDelayInMinBetwnReqBeforeReinstating 25
zmprov mcf zimbraInvalidLoginFilterMaxFailedLogin 5
zmmailboxdctl restart

More info on Zimbra Wiki: https://wiki.zimbra.com/wiki/DoSFilter