When comparing Opera Mail vs Mail and Calendar, the Slant community recommends Mail and Calendar for most people. In the question“What are the best e-mail clients for Windows?” Mail and Calendar is ranked 3rd while Opera Mail is ranked 7th. The most important reason people chose Mail and Calendar is:
Mail and Calendar support multiple accounts from multiple services, including Gmail and Google Apps. Gmail and Google Apps support was not available on Windows 8. It is available on the Windows 10 version of Mail and Calendar app.
Specs
Question Ranking
Pros
Pro Opera Mail CAN BE set as default email client in Windows 8 & 10
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.
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 Intuitive user interface
The design of the UI in Opera Mail is clean and intuitive, making for an easy to use client.
Pro Supports multiple services including GMail
Mail and Calendar support multiple accounts from multiple services, including Gmail and Google Apps. Gmail and Google Apps support was not available on Windows 8. It is available on the Windows 10 version of Mail and Calendar app.
Pro Send email from Outlook.com aliases
An alias is a great feature for keeping your email private
Pro Drag and drop calendar events to reschedule them (PC only)
If you like using a calendar, this is an efficiency perk.
Pro Swipe functionality
If your device has a touchscreen, then user can swipe the message thread either from left or from right, varies by swipe preferences set by user, eg: set swipe from right to delete and swipe from left to archive.
Pro Background wallpaper
Similar to Yahoo! Mail and Gmail web app, Mail app can allow users to set any images as image background of the app.
Cons
Con Sync is slow
Opera tends to be slower on e-mail sync when compared to other popular clients.
Con Missing some advanced features
The Mail app is missing some advanced features that can be found in other products such as automatic template replies, email filters and custom notification sounds.
Con No custom signature with HTML or images
You will miss the option to customize the signature with HTML content and images.