So I searched a bit about what is the best mail client. BTW I use Ubuntu Linux. So Outlook etc is not at all an option for me. I used Opera even when I was using Windows XP also.

The only alternative I got is Thunderbird. Then I started using thunderbird for 4 days. After 4 days of use, I felt like my Opera is much better than this. Here is what I found.

Advantages of Thunderbird over Opera:

1. Rich Text Editor for composing mails
2. Support Digital Certificates
3. You can use Filters to move an incoming mail to “Sent” folder.
4. Custom Labels
5. Open any mail as new in Compose View

Disadvantages:

1. Slow
2. No Attachments Filters
3. No Labels Filters
4. No way to see yesterdays messages
5. No way to see messages sent by a contact
6. Add to Contacts list sucks, It doesn’t even check duplicates
7. No customization of Toolbar
8. No Browser, You need to launch Firefox to see any link in the mail.
9. No Saved Searches
10. No integrated contact list
11. No Filters as Folders

I have realised that Opera is much much better than Thunderbird if you check mails more than 10 times a day. If you check only once and do not have any filters, use Thunderbird.

Finally I switched back to Opera.