Unibox vs Opera Mail
When comparing Unibox vs Opera Mail, the Slant community recommends Opera Mail for most people. In the question“What are the best e-mail clients for macOS?” Opera Mail is ranked 9th while Unibox is ranked 17th. The most important reason people chose Opera Mail is:
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.
Specs
Question Ranking
Pros
Pro Simple, clean interface
Unibox's interface is very clean and easy to understand. It has a classic two-pane interface with all users that have sent emails on the left side and any email currently being read on the right.
Every UI element is only visible when needed. For example, every time you hover on a discussion the trash can, which is otherwise invisible appears.
Pro All emails are sorted by contact
Pro Makes it easy to keep track of different discussions
Unibox groups different emails by user instead of subject. This makes it easy to keep track of messages sent to a particular person and to keep track of different discussions.
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.
Cons
Con Sends empty emails
Other than syncing issues and displaying wrong badge numbers, Unibox sometimes sends empty emails to people in the user's contact list, which is quite annoying.
Con A number of recurring issues
There are some recurring issues with Unibox: these include the sync dropping and e-mails not reaching their destination.
Con Always needing to update token for Gmail
Con Very limited feature set
Compared to Thunderbird.
Con Sync is slow
Opera tends to be slower on e-mail sync when compared to other popular clients.