Free S/MIME Certificate: Who Still Offers One, and the Catch

Which free S/MIME certificates still exist?

Four routes are usually called free, and only one of them gives you an S/MIME certificate that other people's mail apps accept without any setup on their side: Actalis's Mailbox Validated certificate, free for its first year. A self-signed certificate and a CAcert certificate cost nothing but are not trusted by default, and Let's Encrypt does not issue email certificates at all. We checked each option against the provider's own pages and the public root lists on October 13, 2026.

Older guides still send readers to a free Comodo email certificate. Comodo's certificate business is now Sectigo, which stopped issuing its old-format S/MIME certificates on August 28, 2023, ahead of the CA/Browser Forum's S/MIME Baseline Requirements, and Sectigo's S/MIME product page lists no free certificate today. Some reseller pages go the other way and say free email certificates no longer exist at all; Actalis shows that isn't so, with conditions.

What does the free Actalis certificate include?

Actalis's free S/MIME certificate is a Mailbox Validated certificate: Actalis checks that you control the email address and nothing else. As of October 13, 2026, its product page lists it as "Free / First year", renewing at €6.00 + VAT a year, with one free certificate per email address per account; further certificates for the same address are paid. The page offers one- and two-year durations.

"Mailbox validated" also limits what the certificate can say. The S/MIME Baseline Requirements (version 1.0.16, §1.2) limit the subject of a mailbox-validated certificate to an optional email address, common name and serial number, and §7.1.4.2.2 says the common name, if present, holds the mailbox address. Organization names, given names and surnames are not allowed. So a recipient checking your signature sees an address that has been confirmed, not a person or a company. For many personal uses that is enough; for a business sending invoices, it usually isn't.

The term is capped too. Under §6.3.2 a Strict or Multipurpose S/MIME certificate may last at most 825 days, and CAs have not been allowed to issue under the longer-lived Legacy profiles since July 15, 2025. Any S/MIME certificate, free or paid, therefore means a renewal at least every two years and three months.

Who generates the private key on a free certificate?

For its free S/MIME certificates, Actalis generates the private key and delivers it to you in a PKCS#12 file, according to Actalis's own FAQ, which adds that under its Certificate Policy Actalis does not keep the key after sending it. The S/MIME Baseline Requirements allow this (§6.1.1.3 says a CA "MAY generate the Private Key on behalf of the Subscriber"). The alternative, offered by CAs that accept a certificate request, is to create the key yourself and send only the public half.

What a CA-made key costs you is control over its birth. You can't generate it on a smart card or hardware token, and it existed outside your device before it reached you. The rules compensate with transport protection: §6.1.2 says a key the CA sends you must travel either in hardware with a separately delivered activation password, or encrypted with at least 112 bits of strength, for example a PKCS#12 file whose password and algorithm together reach that level. You can check what you received. We built two PKCS#12 files from a throwaway key with OpenSSL 3.0.13 on October 13, 2026, one with current defaults and one with the -legacy option, and asked OpenSSL to describe them:

$ openssl pkcs12 -in modern.p12 -info -noout -passin pass:test123
MAC: sha256, Iteration 2048
MAC length: 32, salt length: 8
PKCS7 Encrypted data: PBES2, PBKDF2, AES-256-CBC, Iteration 2048, PRF hmacWithSHA256
Certificate bag
PKCS7 Data
Shrouded Keybag: PBES2, PBKDF2, AES-256-CBC, Iteration 2048, PRF hmacWithSHA256

$ openssl pkcs12 -in legacy.p12 -info -noout -passin pass:test123
MAC: sha1, Iteration 2048
MAC length: 20, salt length: 8
PKCS7 Encrypted data: pbeWithSHA1And40BitRC2-CBC, Iteration 2048
Error outputting keys and certificates
... unsupported ... Algorithm (RC2-40-CBC : 0)

$ openssl pkcs12 -in legacy.p12 -info -noout -passin pass:test123 -legacy
...
Shrouded Keybag: pbeWithSHA1And3-KeyTripleDES-CBC, Iteration 2048

The "Shrouded Keybag" line is the one that matters: it names the algorithm protecting the private key. OpenSSL 3 writes AES-256 under PBKDF2 by default. In the legacy file, 40-bit RC2 protects only the certificate and Triple DES protects the key, and OpenSSL 3 won't open the file at all without the -legacy option. (The password is a throwaway one for this test; without -passin, OpenSSL asks for it.) Run the same command on any key file a CA sends you; we have not obtained an Actalis file ourselves, so we can't tell you which line theirs prints. Keep the password and the file in separate places, and delete the email or download that carried the file once it is safely imported and backed up.

Will recipients' mail apps trust a free Actalis certificate?

Recipients' mail apps trust an Actalis certificate when its chain ends at an Actalis root that their trust store accepts for email, and Actalis now has more than one such root. Its older "Actalis Authentication Root CA" is trusted for email by Mozilla (trust bits "Websites;Email") and by Microsoft (with Secure Email among its uses), and it is on Google's list of CAs that Gmail trusts for hosted S/MIME.

Actalis also has dedicated S/MIME roots valid from February 28, 2025, "Actalis SMIME RSA Root CA 2025" and an ECC twin. Microsoft's root list includes both for Secure Email. Mozilla does not yet: Actalis's request to add them (Mozilla bug 1992971) was still open on October 13, 2026, and Google's Gmail list names only the older root. We could not confirm which root a newly issued free certificate chains to, so check yours before relying on it in Thunderbird, which ships with Mozilla's root store, or in Gmail hosted S/MIME. These two commands print the subject and issuer of every certificate in the file Actalis sends you:

openssl pkcs12 -in yours.p12 -nokeys | grep -E "^(subject|issuer)="
openssl pkcs12 -in yours.p12 -nokeys | openssl x509 -noout -subject -issuer -enddate

The issuer at the top of the chain tells you which root you depend on. Gmail's hosted S/MIME requires a chain that anchors to a CA "explicitly trusted by Google for this purpose", though a Workspace administrator can add roots for a domain; our Google Workspace S/MIME setup guide covers that upload and the editions that offer hosted S/MIME.

Why not a self-signed or CAcert certificate?

A self-signed or CAcert certificate is free and signs mail perfectly well, but the signature only checks out for people who have chosen to trust that certificate or root by hand. We made a self-signed S/MIME certificate with OpenSSL 3.0.13 on October 13, 2026, signed a short message with it and verified the result the way a recipient's software would, against its default trust store:

$ openssl cms -verify -in signed.eml -out /dev/null
CMS Verification failure
...:certificate verify error:...:Verify error: self-signed certificate

$ openssl cms -verify -in signed.eml -CAfile self.crt -out /dev/null
CMS Verification successful

The same signature passes only once the recipient supplies the certificate as a trust anchor, which is what "importing it by hand" means in a mail app. CAcert moves the problem up one level: its root is in neither Mozilla's nor Microsoft's list of included root certificates, so every recipient would have to install CAcert's root first. Between two or three people who swap certificates once, that is workable. For mail to customers or suppliers, every recipient who hasn't done that sees a signature their mail app can't verify.

What does a free S/MIME certificate cost after the first year?

Actalis's free certificate costs €6.00 + VAT a year from the second year, so over three years you pay for two. That sum is small; the time spent each renewal is the larger cost. Each new certificate has to be imported into every mail app and phone you sign from, and your correspondents pick up the new certificate from your next signed message.

Plan for the old key as well. Mail that was encrypted to you can only be opened with the private key it was encrypted for, so if a renewed certificate comes with a new key pair, keep the old PKCS#12 file and its password. Losing it locks you out of your own archive. Our guide to what S/MIME expiry does to old mail walks through keeping both.

Free or paid S/MIME certificate: which should you pick?

Pick the free Actalis certificate when you want signed and encrypted mail on a personal address and showing only that address is fine. Pay when the certificate has to show who you are, when policy says you generate and hold the key yourself, or when you need a predictable renewal for several mailboxes. The table maps common situations to a choice.

Identity is the line a free certificate can't cross. Individual validation adds your name, organization validation adds the company, and sponsor validation adds both; the guide to S/MIME validation types lists the checks behind each. At My-SSL, the Individual plan validates the email address and the Business plan also validates the organization and puts the company name in the certificate, both on the S/MIME certificate page. If you only need a confirmed address for personal mail, the free year from Actalis does that job.