I've read mixed reports for Opera as a web browser and their email
client. I've used Firefox and Thunderbird - their excellent plugins give
them a great advantage over alternatives. I have to say for four years
none of the others have been worth considering IMHO. I receive a
considerable amount of email and to mention one plugin i couldn't live
without ImportExportTools - used to back up each years emails. No other
email client offers such flexibility.