This is a fantastic feature of Thunderbird, although does tempt you to have too many mails open at once. Tabs in general are a very big part of Thunderbird and like Firefox, you can have multiple messages open in separate tabs. Search results are displayed in a separate tab. The search tool in Thunderbird is excellent and searches happen in real time as you type.
Nowadays, this is a little outdated because many people use a separate application - or even Firefox itself - to follow RSS feeds but it may be useful if you only want to mail and follow RSS feeds at the same time when composing mails. What makes Mozilla Thunderbird slightly more unusual is the fact that it comes with an integrated RSS reader. And of course, there's a built-in spell checker to make sure that your mails are professionally crafted. To stay well organized, Mozilla Thunderbird offers filters to deliver your mail into separate folders and inboxes. You can quickly import your mail and contacts from your Outlook or Mail account and set up POP3, IMAP or SMTP accounts in a flash. Setting up Mozilla Thunderbird is painless. It's also now much faster and more stable than before due to the Gecko 5 engine. The fact that like Firefox, Mozilla Thunderbird can be beefed up with all manner of extensions makes it an extremely competitive mail client.