eM Client vs Thunderbird
Both are bought outright, both sit in email & tasks, and both are bought by people leaving Mimestream, Spark Premium, Superhuman. Here is what actually differs — including what each price does not buy.
The short answer
- Thunderbird is free; eM Client costs €39.95.
- eM Client has the cleaner licence: buy once, own forever, against free and open source for Thunderbird.
Side by side
 eM Client€39.95Perpetual |  ThunderbirdFreeOpen source | |
|---|---|---|
| What it is | mail, calendar and contacts client whose one-time licence covers future versions | free mail, calendar and contacts with no tier above it |
| Price | €39.95 | Free |
| Licence | Buy once, own forever | Free and open source |
| What you get | One payment. Updates included, indefinitely. | No licence to buy, and the source is public. |
| The catch | VIP Support is free for the first year only, then needs a paid extension | Nothing to pay, but it is a cross-platform app that never quite feels Mac-native |
| Macs per licence | 3 | not established |
| Account required | no | no |
| Works offline | partly | partly |
| Apple Silicon | No | Yes |
| Free trial | Yes | No |
| On Setapp | No | No |
| Minimum macOS | not established | not established |
| App Store rating | not established | not established |
| Last updated | not established | not established |
| Price checked | 2026-09-22 | 2026-09-22 |
Apple’s public API reports a rating for only a small minority of Mac apps, and returns zero for most of the rest even when the store page plainly shows reviews. A blank here means we could not read a number, never that an app is unrated or disliked.
In their own right
eM Client
A desktop mail client that also does calendar, contacts, tasks and chat, with PGP and S/MIME built in. The one-time Personal licence includes Lifetime Upgrades, so it stays valid for future major versions rather than only the one you installed.
Thunderbird
The open-source desktop mail client, with a calendar, an address book and OpenPGP encryption built in. Free forever on the desktop, funded by donations rather than seats.