When comparing Claws Mail vs Opera Mail, the Slant community recommends Claws Mail for most people. In the question“What are the best e-mail clients for Windows?” Claws Mail is ranked 8th while Opera Mail is ranked 10th.
Ranked in these QuestionsQuestion Ranking
Pro Has many plugins for extra functionality
Pro Low resource client
Claws Mail is a low resource e-mail client that is often default in low resource Linux distributions.
Pro Clean interface with 5 layout variants
Pro Good support for Google's services
Pro Saves emails in uncompressed readable format
Allows one to read archived emails with a text editor.
Pro Free and based on Mozilla code
Opera Mail is completely free to download and use and it is based on Mozilla's code, which is what makes it a bit similar to Thunderbird in looks and function.
Pro Opera Mail CAN BE set as default email client in Windows 8 & 10
Pro Intuitive user interface
The design of the UI in Opera Mail is clean and intuitive, making for an easy to use client.
Pro Automagic smart filtering
After a bit of use Opera learns what e-mail belongs in what folder just by previous usage. This makes for a convenient way to have e-mails filtered without having to manually mange every e-mail.
Con Saves emails in uncompressed format
This takes more space on the HDD.
Con Interface looks old and setup is not easy
The icons as well as the rest of the interface look like an application from the early 90's, with this there is also no easy setup options built in like the more modern e-mail clients.
Con Very limited feature set
Compared to Thunderbird.
Con Being discontinued
Opera Mail will be end of lifed per Opera website
Con Sync is slow
Opera tends to be slower on e-mail sync when compared to other popular clients.