When comparing Opera Mail vs Nylas 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 8th while Nylas Mail is ranked 14th.
Ranked in these QuestionsQuestion Ranking
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 Great design
Simple, easy to use, easy to learn user interface.
Pro Open Source
You can change it, customize it, and make plugins for it.
Currently there are plugins for GitHub integration, Templates, and Translation, and the potential for many more to come. It's built on top of Chromium so making plugins for it will not only be easy for Chrome app and extension developers, but it means that it has the potential to use Chrome plugins, too.
Pro Dynamic, secure, private
You can use Nylas' servers, or run your own mail server on your own computer.
Pro Works with Exchange accounts
N1 is one of the few 10 Windows Desktop Clients to offer support for a business Exchange email account (the Windows Native Client is one of the few alternatives that also work). It seems that this niche is really dominated by Outlook, and few solutions are available that prioritize it.
Con Very limited feature set
Compared to Thunderbird.
Con Does not support 4K monitors
Con Sync is slow
Opera tends to be slower on e-mail sync when compared to other popular clients.
Con Some features require a monthly subscription
Con A lot of RAM memory used
This email client uses a lot of RAM (random access memory) - actually using more than Chrome (albeit with a lot of tabs open).
Super slow to sync. not really supported anymore as they're focusing on their API.