Thunderbird vs eM Client Pricing: Free, Perpetual or Subscription?

Thunderbird vs eM Client pricing is not a close comparison on money, and pretending otherwise wastes your time. Thunderbird is free software funded by donations, with no paid desktop tier at all. eM Client gives away a restricted version and sells the rest, in two licence shapes and two payment models.

So the interesting question is not which is cheaper. It is what eM Client's money buys you, whether that is worth paying for in your situation, and which of its two payment models costs less over the three-to-five-year life of a desktop client. This post answers all three, and sends you to each vendor's own page for the actual figures.

The verdict up front#

Thunderbird is cheaper. It is cheaper today, cheaper in year five, cheaper for one person and cheaper for a twelve-person office, because the number it charges is zero and stays zero. There is no seat count, no device count, no commercial-use clause and no renewal. If price is the deciding criterion, the comparison ends here.

eM Client wins on a different axis, and it is worth naming plainly: the paid version is a more finished product for people who live in a mail client all day. Snooze, undo send, send later, watch-for-reply, tracking-pixel blocking, a signature library and per-message translation are all things eM Client ships and charges for. Thunderbird covers some of that only through add-ons, and some not at all.

The honest recommendation: if your objection to eM Client is the price, use Thunderbird and you will lose very little. If your objection to Thunderbird is the rough edges, eM Client's licence is a small, one-off amount of money against the hours you spend in email — and its one-time payment option means it need not become a recurring bill.

Thunderbird vs eM Client pricing at a glance#

This table is about packaging shape, not amounts. Read it as the set of questions each vendor's pricing page will ask you.

Where Thunderbird wins: there is nothing to buy, ever#

Thunderbird is developed by MZLA Technologies Corporation, a wholly owned for-profit subsidiary of the Mozilla Foundation, and its own donation page states that nearly all of Thunderbird's operating revenue comes from user gifts. The download page carries the words "Free forever" under the button. That is the whole pricing model.

Two details matter more than people expect. First, it is free for business use — the donation FAQ says so in those words. A ten-person office can install it on ten machines and owe nothing, which is not true of most clients that describe themselves as free. Second, it is open source under MPL 2.0, so the licence cannot be withdrawn from the version you already have.

That combination is what makes it the cheapest desktop email client for a small office by a wide margin. Not the cheapest paid one — the free one that has no asterisk attached to commercial deployment.

• No seat count, no device count, no renewal date.
• Free for commercial and personal use alike, per Mozilla's own FAQ.
• The only desktop client of the two with a Linux build.
• Organisations that want to contribute do so through a Corporate Supporter donation channel — a gift, not a licence fee.

Where eM Client wins: the paid features are the product#

Concede this one outright: eM Client's paid version does things Thunderbird does not do out of the box, and several of them are the small daily conveniences that decide whether a client feels modern. Its own feature comparison shows what the free tier withholds, and the list is the giveaway.

Crossed out on the free tier: thread view, snooze, undo send, send email later, watch for reply, blocking of tracking pixels, mass mail, notes on an email, automatic translation of incoming messages, an attachments view, quick actions, Teams and Slack integration, profiles, and the signature and QuickText libraries. Those are not enterprise extras. That is the daily surface of the client.

So the free tier of eM Client is best understood as an extended demo with no deadline rather than a product. The real comparison is Thunderbird against eM Client's paid tiers, and there the money is buying convenience and polish rather than capability you cannot otherwise reach.

Free, perpetual or subscription: the three money models#

The headline question hides a second one. Thunderbird offers one model. eM Client offers two, and the choice between them changes the long-run number more than the choice of tier does.

Perpetual licence vs subscription: which is cheaper?#

For a desktop email client, the perpetual option is almost always the better buy, and eM Client is unusual in still offering one. A mail client is not a service you consume; it is a tool you install and then keep using for years. Paying once for something you will run until the hardware dies is the shape that matches the use.

Two asymmetries are worth knowing before you pick. On the one-time payment, VIP support is time-boxed to one year while upgrades are described as lifetime — so you keep getting new versions but stop getting priority help. And the AI Add-on, which is bundled into the subscription, remains a separate purchase on the perpetual route.

That means the honest comparison is not subscription versus perpetual at equal scope. It is subscription-with-AI versus perpetual-without. If you have no interest in the AI features, the perpetual option is straightforwardly cheaper the moment you pass its break-even against the annual renewal. If you do want them, price the add-on before you decide.

Is eM Client free for business use?#

No. This is the single most misread line on its pricing page, so it is worth stating flatly. The free tier's commercial-use row reads "None". The Personal licence is marked "Individual use only". Company and institutional use requires the Business licence.

The two tiers are also licensed differently, which matters more than the price gap between them. Personal covers one user across up to three devices. Business is licensed per device, with the quantity driving a volume discount, and it is the only tier that includes the License manager for administering those seats.

So a freelancer running two mailboxes on one laptop can technically stay on the free tier only if the work is non-commercial — which for a freelancer it is not. In practice, any business use of eM Client is a paid use. Thunderbird has no equivalent clause, and for a small office that distinction is the entire cost comparison.

What does Thunderbird Pro cost, and does it change the answer?#

Thunderbird now has a paid product, and it confuses this comparison unless you separate the two things. Thunderbird Pro — increasingly marketed under the name Thundermail — is a set of hosted services, not a licence for the desktop client. It bundles Thundermail email hosting, an Appointment scheduling tool and Send for large encrypted file transfers into one subscription.

As of September 2026 it is still in beta, released in waves to a waitlist, with a full launch expected during 2026 and a single plan on the page named the Early Bird Plan. The servers are in Germany, it speaks JMAP alongside IMAP and SMTP, and a Thundermail account works in any mail program, not only Thunderbird.

The part that matters here: the desktop client stays free regardless. Thunderbird Pro is Thunderbird competing with your email host, not with eM Client's licence. If you already have a mailbox you are happy with, it changes nothing about what Thunderbird costs you.

Who each one is genuinely for#

Price alone decides fewer cases than you would think, because the free option here is genuinely capable. What actually separates the two is platform, account count and how much the daily conveniences are worth to you.

A third option, honestly — and we build it#

We build AI Emaily, so treat this section as what it is: the vendor's own pitch, placed at the end because it does not belong in the cost comparison above. On the question this post asks — what is cheapest over five years — we lose to both of them, and we are not going to pretend otherwise. AI Emaily is a subscription. There is no permanent free tier, only a 7-day free trial on Pro and Autopilot, card required, and nothing charged if you cancel before day seven.

Where it belongs in the conversation is the last row of that table. Neither Thunderbird nor eM Client's licence gets you an agent that triages the inbox, drafts replies from a Context brain you write yourself plus per-client profiles, and closes loops across Gmail, Outlook and plain IMAP in one place. eM Client sells AI as an add-on; Thunderbird ships none at all. If that is the gap you are actually trying to close, a licence for either client will not close it.

The limits, stated plainly: no Linux build, macOS is Apple Silicon only and is an Electron shell rather than a native binary, and Android is a PWA rather than a native app. Every agent action is approve-before-send in Copilot, with undo and an audit trail, and we do not train on your mail. If cost is the deciding factor here, buy neither of those things and use Thunderbird — that is the right answer and we will say so.