Recently, we have received some external emails that attempt to impersonate some of our colleagues for fraud.
For example, when you receive an email from "Boss <email@example.com>",
Zimbra will show Boss by default and you have no idea you will be replying to firstname.lastname@example.org.
In order to ensure that the full email address is also shown, please do the following:
Go to Preferences > General: Under Others, untick Email Addresses option
This will also be useful when you have senders that happen to share a common name.