Thunderbird
Close matchFreeThe steadier option if you want something that will still be updated in five years. Less polished to look at, more features under the surface.
Your files: Connects to the same accounts over IMAP. Imports contacts as .vcf.
Does Mailspring run on Linux?
Verdict: Yes
Yes. Mailspring publishes Linux downloads next to the Windows ones, including Flatpak, .deb and .rpm files and a Snap listing, so the same app carries straight over.
The Mailspring download page lists Windows, Mac and Linux. For Linux it offers a Flatpak, a .deb file for Ubuntu and Mint, a .rpm file for Fedora, and an automatically updating Snap. Flatpak and Snap are both app stores built into most Linux systems, so for most people this is a search and a click.
Your accounts set themselves up again. Mailspring connects to Gmail, Outlook.com, iCloud and ordinary IMAP accounts, and because the messages sit on the mail server, signing in on Linux brings the inbox and the folders back as they were.
The paid Pro features work the same way. They are tied to your Mailspring account rather than the computer, so signing in restores them with no second payment.
One honest caution. Mailspring is a small project and updates arrive when they arrive, so if your mail is business critical, Thunderbird is the more conservative choice on Linux and has a much larger group of people maintaining it.
Mailspring on Linux, and alternatives
Geary
Close matchFreeSimilar clean look to Mailspring and built into the Ubuntu and Fedora app stores. Mail only, no calendar.
Your files: Mail comes from the server, nothing to convert.
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