So, if you're trying to access a Zimbra email file that MS Outlook can't open, don't worry; There is definitely a solution. For starters, it's important to note that Zimbra uses a special file format (.tgz) that Outlook won't immediately recognize. To avoid this issue, use a third-party converter application such as SameTools TGZ to PST Converter to convert the Zimbra file to an Outlook-compatible format, such as.pst or.msg Once all the files are converted, you can open them in Outlook without any much trouble.