My vote goes to HandyBackup and MailStore Home.
I used these applications at two different points in time. And they are the best, safe and reliable options for SMBs.
Granted there are other companies that offer better mail backup applications but they expensively priced as well.
Before going to the Software you are looking for, I am telling you why you need software. In manual methods, we are facing many problems like a time-consuming process, not select multiple emails at a time, Duplicate files can be generated, etc.
We have seen many drawbacks of manual methods so, to resolve all these drawbacks we need a method called software method i.e, Email Backup Software.