Thunderbird is my favorite email client – I use it on daily basis. The nice thing about it is that it allows me to set up as many email accounts as I want and each email account is separate from others and has its complete set of folders such as Inbox, Drafts, Sent, Trash, Outbox, etc for each account. Also I can create a custom folder within each folder if I want to.
The following are descriptions that come with the application and users reviews:
The Mozilla Thunderbird email client.