Our estimation of 'minimum' changes over time, as evildoers get more sophisticated…
For the moment, this is our recommended minumum:
From the Zimbra Web Client:
ZWC → Preferences → General → Password
ZWC → Preferences → Accounts → Password Recovery Account Settings → Add Recovery E-Mail
Access your Recovery E-Mail account to obtain the verification code.
Enter the verification code in Zimbra to complete the process.
If you have trouble with copy and paste, try manually entering the verification code.
You can now use the Forgot Password
link on the Zimbra login page to reset your password.