A certified email is an email sent through a trusted third party that time-stamps the sending, the delivery and the content, and issues a verifiable evidence certificate. Under Article 43 of the eIDAS Regulation, it cannot be denied legal effect or admissibility as evidence for being electronic. In almost every private communication it replaces registered post, which in Spain, for example, costs from €8.71 to €36.01 per burofax under the Correos 2026 tariff.
Why an ordinary email is no use to you as evidence
An ordinary email does not prove that it arrived, what it said or when, the moment the other party denies it. National civil procedure rules on private documents follow the same logic across Europe; in Spain, Article 326 of the Civil Procedure Act puts it plainly: if the opposing party disputes the authenticity of a private document, whoever produces it has to prove it. And with an ordinary email you cannot, for three reasons any forensic expert will explain in five minutes:
- The date comes from your own server. You control the clock of the system that sends the email. A date set by the party with an interest in that date is not evidence, it is an assertion.
- The content is not fixed. Nothing stops a message in the Sent folder from being edited or reconstructed. Without a digital fingerprint of the original content, you cannot prove that what you are showing is what went out.
- There is no record of delivery. Leaving your server does not mean it entered the recipient's. Read receipts are voluntary and most mail clients block them.
In practice the problem does not surface the day you send. It surfaces eighteen months later, when the matter reaches a court and you find you have a Sent folder and no proof. That is why the notices that matter have always gone by registered post. The point is that today there is a way to get the same proof in seconds and at a fraction of the price.
What a certified email is and what the trusted third party does
A certified email is an email that passes through a trust service provider acting as a technical witness: it records every milestone of the sending, time-stamps it, fixes the content with a digital fingerprint and issues an evidence certificate. The eIDAS Regulation defines it as an electronic registered delivery service (Article 3(36)): a service that makes it possible to transmit data between third parties by electronic means and provides evidence relating to the handling of the transmitted data, including proof of sending and receiving, while protecting the data against the risk of loss, theft, damage or unauthorised alteration.
What changes compared with an ordinary email is not the email; it is who vouches for it:
- Timestamping. The date and time of every event is set by an eIDAS trust service provider, not by your server.
- Content hash. A fingerprint (SHA-256) is calculated for the subject, the body and every attachment. If a single character is changed afterwards, the fingerprint no longer matches and the tampering is exposed.
- Delivery record. Acceptance by the recipient's server is logged and, where their mail client allows it, so are opening and attachment download.
- Signed certificate. All of the above is compiled into an electronically signed PDF that any third party can verify without asking the provider for anything.
The recipient receives an ordinary email in their inbox. They do not register on any platform or accept anything. You can choose whether the message carries a visible notice that it is certified, which tends to speed up replies, or stays discreet.
Payment demands, letters to employees, changes of terms, GDPR responses. If the answer is "several" and today they go out by ordinary email, bring them to a 20-minute session and we will build the workflow that sends them certified and files the evidence in the case record.
What legal validity a certified email has in the EU
It has the validity of admissible evidence whose weight depends on the quality of that evidence, exactly like registered post. The basis rests on three layers of law:
| Rule | What it says | What it means for you |
|---|---|---|
| eIDAS, Article 43 | Data sent and received using an electronic registered delivery service shall not be denied legal effect or admissibility as evidence solely because it is in electronic form (43(1)). Data sent and received using a qualified service enjoys the presumption of integrity, of sending by the identified sender, of receipt by the identified addressee and of accuracy of the date and time (43(2)). Applies directly in every EU Member State. | Nobody can reject your evidence "because it is an email". If the service is qualified, it is also the other side that has to rebut it. |
| National implementing law (in Spain, Law 6/2020) | Each Member State implements eIDAS domestically: obligations and supervision of trust service providers. | The provider that seals your email is under administrative supervision; it is not just any witness. |
| National civil procedure rules (in Spain, Civil Procedure Act, Arts. 299, 326 and 382) | Electronic documents are a means of evidence; if they are disputed, whoever produces them must prove their authenticity. | The hash, the timestamp and the signature on the certificate are exactly what you need when your evidence is challenged. |
One point worth being precise about: the law does not say a certified email is "equivalent" to registered post. It says neither can be rejected, and that in both cases the court weighs the evidence. Because the evidence of a certified email includes the full content and the attachments, something registered post only provides if you pay for content certification, in practice it is usually the more complete proof.
Certified email vs registered post: price, time and proof
Registered post remains valid and in some cases mandatory, but it is a postal service with postal-service pricing. Take the Spanish burofax as a reference: under the Correos 2026 tariff for mainland Spain and the Balearics the figures are as follows, and comparable registered-post services in other countries cost similar amounts:
| Criterion | Registered post (Spanish burofax, Correos 2026) | Certified email |
|---|---|---|
| Price per item | €8.71 Premium online; €12.72 at the counter; €36.01 Premium Plus with custody, acknowledgement and certified copy; +€1.27 per additional page | Per item, a fraction of registered post, with no page limit |
| Time until you have proof | 24–48 h; longer if the recipient is absent or refuses | Seconds |
| Proof of content | Only with content certification (add-on service) | Always, with a hash of the message and the attachments |
| Attachments | Printed pages only | PDFs, images and documents, certified together with the message |
| Work for the sender | Print, go to the post office or upload the PDF, pay, file the receipt | Write the email, or nothing at all if the process triggers it |
| When it is the right choice | The law or the contract requires that form; you have no email for the recipient | Private B2B and B2C communications with a known recipient email |
An accounting firm that sends forty payment demands a month pays between €348 and €509 in burofax fees at Spanish rates, before counting the hours. With certified email the same volume costs a fraction and, above all, goes out on the day it is due, not when someone has a gap in their diary to go to the post office.
When certified email is enough and when you still need registered post
It is enough for any private communication where you need to prove sending, content and date to someone whose email address you know. The most common cases:
- Debt collection. Staged payment demands at 15, 30 and 60 days with the invoice attached. A formal demand with proof of date fixes the start of late-payment interest and underpins any later court claim.
- Employment communications. Employment law in many member states requires written notice of dismissal and of serious disciplinary sanctions, stating the facts and the effective date, without prescribing a specific medium; in Spain that is Articles 55.1 and 58.2 of the Workers' Statute. Also the end of fixed-term contracts, substantial changes to working conditions, formal summonses and payslip delivery.
- Customers and contracts. Price increases, changes of terms, notice of non-renewal, termination for breach. What is always in dispute here is whether notice was given in time: exactly what the timestamp settles.
- GDPR. Responses to data subject requests within the one-month deadline and breach notifications to affected individuals. If you handle these requests through a workflow, see how to respond on time without requests getting lost in a mailbox.
- Suppliers and property. Non-conformities, order cancellations, demands to tenants, rent reviews, notices to owners' associations.
You still need registered post, a notarial letter or personal service when:
- A rule or the contract itself expressly requires that form of notice.
- You do not have an email address that can be treated as the recipient's own (the one in the contract, the one they habitually use with you).
- The recipient is a public authority that serves and receives notices through its own official electronic channel (in Spain, under Law 39/2015).
- The act requires a notarial deed.
What the evidence must contain to survive a challenge
Not all "certified emails" are equal, and the difference shows on the day the other party disputes it. Before signing up to any service, check that the evidence certificate includes:
- Authenticated sender and recipient exactly as sent, with no aliases that later need explaining.
- A timestamp from an eIDAS trust service provider on every event, not the mail server's clock.
- A hash of the subject, the body and every attachment, and the full content embedded in the certificate.
- The technical delivery record: the destination server's response and, where it exists, opening and download.
- An electronic signature on the certificate itself, so an expert can verify it with a PDF reader without depending on the provider.
- Custody with a retention period and free export. Retention and limitation periods vary by country. In Spain, for example, personal actions become time-barred after five years (Article 1964 of the Civil Code) and Article 30 of the Commercial Code requires business correspondence to be kept for six years. If you stop being a customer, the evidence must remain verifiable.
And one question almost nobody asks, which decides half of all disputes: where is that PDF going to be three years from now? If the answer is "in the mailbox of the person who sent it", you already have a problem, however perfect the certificate.
How Dokuflex solves it: certified email as a step in the process
Dokuflex, the low-code BPM platform with AI, includes certified email as one more action in the process designer. The difference from a stand-alone service is not in the certificate, which is equivalent, but in everything that happens before and after:
- It fires only when it should. Invoice 30 days overdue, GDPR request five days from the deadline, contract with notice due in 60 days: the Dokuflex BPM workflow composes the email from a template with the case data, attaches the generated document and sends it certified. Nobody has to remember.
- The evidence stays in the case record. The certificate is filed in the document management system alongside the contract, the invoice or the employee file, with permissions, a retention period and a deletion lock. When the lawyer asks for it, it is where it should be.
- Notify and sign in the same workflow. If you also need the recipient's agreement, the same flow sends the document for eIDAS electronic signature. On how much that step saves, see the ROI of electronic signature.
- AI reads the reply. An AI action classifies what the recipient answers (payment, dispute, silence) and moves the case to the next step, with human validation when confidence falls below the threshold. It is the same logic we explain in from prompts to processes.
- It is sent from where you already work. A REST API and integrations with your ERP or CRM so the demand goes out from the customer record, not from a separate tab.
A real example of a debt collection workflow: on day 15 an ordinary reminder goes out; on day 30, a certified email with the invoice and the interest calculation; on day 60, a second certified demand warning of legal action plus a task for the account owner to decide whether to hand it to the lawyer, with both certificates already in the case record. Building it takes under an hour with the process templates.
Create your free account and send your first certified email today →
Frequently asked questions
Is a certified email legally valid? +
Yes. Article 43(1) of Regulation (EU) No 910/2014 (eIDAS) states that data sent and received using an electronic registered delivery service shall not be denied legal effect or admissibility as evidence solely on the grounds that it is in electronic form. It applies directly in every EU Member State; in Spain, for example, it is complemented by Law 6/2020, and national civil procedure rules admit electronic documents as evidence. What a court weighs is the quality of the evidence: who sent it, to whom, with what content and when.
What is the difference between a certified email and registered post or a burofax? +
Both prove sending and date and, with the add-on services, content and delivery. Registered post is a paper-based postal service: the Spanish burofax, for example, costs from €8.71 online and €12.72 at the counter under the Correos 2026 tariff, up to €36.01 with custody and a certified copy, and takes one or two days to deliver; comparable registered-post services in other countries cost similar amounts. A certified email is delivered in seconds, includes the attachments in the evidence, costs a fraction and can be triggered automatically from a process. Registered post is still required when the law or the contract demands that specific form, or when you do not have the recipient's email address.
Why is an ordinary email useless as evidence? +
Because once the other party disputes it, national civil procedure rules on private documents (in Spain, Article 326 of the Civil Procedure Act) put the burden of proving authenticity on whoever produces it, and an ordinary email gives you no independent way to prove that it was sent, that it arrived, exactly what it said or when. Headers can be altered and the server clock is controlled by the sender. A certified email solves this with a trusted third party that time-stamps every event and fixes the content with a hash.
What must the evidence of a certified email contain? +
Identified sender and recipient, the date and time of every event with a timestamp from a trust service provider, the full content of the message and attachments with their digital fingerprint (SHA-256 hash), the technical record of delivery to the recipient's server and, where the mail client allows it, of opening and download, and the electronic signature of the certificate itself so that any third party can verify it without going back to the provider.
Can I dismiss or discipline an employee by certified email? +
Employment law in many member states requires written notice of dismissal and of serious disciplinary sanctions, stating the facts and the effective date, without prescribing a specific medium; in Spain that is Articles 55.1 and 58.2 of the Workers' Statute. A certified email proves sending, date and content, which is exactly what is disputed when the employee denies having received the letter. Many companies combine it with hand delivery or an electronically signed acknowledgement. Check each case with your employment adviser.
Does the recipient need to register or have an account? +
No. They receive an ordinary email in their inbox with the message and the attachments. They do not have to register, download anything or accept any terms for the sending to be certified. You can choose whether the email displays a notice that it is certified (a useful deterrent) or stays discreet.
When is registered post or a notary still required? +
When a rule or a contract expressly requires that form of notice, when you do not have an email address that can be treated as the recipient's own, when the recipient is a public authority that serves and receives notices through its own official electronic channel, and for acts that require a notarial deed. For every other private communication between companies, with employees or with customers, a certified email is admissible evidence and far cheaper.
Sources
- Regulation (EU) No 910/2014 (eIDAS): Article 3(36), definition of the electronic registered delivery service; Article 43, legal effects; Article 44, requirements for qualified services.
- Spain — Law 6/2020 of 11 November, regulating certain aspects of electronic trust services (Spanish implementing law).
- Spain — Law 1/2000 on Civil Procedure: Articles 299 (means of evidence), 326 (evidential weight of private documents) and 382 (electronic storage media).
- Spain — Workers' Statute: Article 55.1 (form of dismissal) and 58.2 (sanctions for serious and very serious misconduct).
- Spain — Commercial Code, Article 30, and Civil Code, Article 1964: retention and limitation periods.
- Correos (Spain), Burofax Premium and 2026 tariff for mainland Spain and the Balearics (prices including VAT at the time of publication).
Next time someone says "it never arrived", have the certificate in the case record
Book 20 minutes and bring your three most sensitive communications: debt collection, HR or GDPR. We build the workflow with you that sends them certified at exactly the right moment and files the evidence where your lawyer will ask for it. No commitment.