P7M attachments in Italian PEC

PEC, Italy’s certified email, brings signed filings, invoices and administrative decisions into the mailbox. The message, though, shows several files with opaque names. Opening the first attachment that looks technical is the fastest way to look at the receipt instead of the document. This guide says what each file is and how to reach the sender’s .p7m, on a computer or on a phone.

The three files that almost always appear

The sender’s provider wraps the original message in a signed transport envelope. In the mail client you usually find:

• postacert.eml: the original message, with the writer’s text and attachments.
• daticert.xml: the certification data, including sender, recipient, subject, date and message identifier.
• smime.p7s: the provider’s signature on that transport envelope. It attests passage through the PEC system, not the person’s signature on the contract.

smime.p7s is small and it is not a PDF. If the envelope reader rejects it, or shows content that is not your document, do not insist. You selected the channel signature, not the document. The reader on this site is not a PEC client and it does not verify that transport signature. It verifies the .p7m you hand it.

Where the sender’s attachment is

1. Open the PEC message in the provider’s webmail or in the mail client.
2. If you see only the outer envelope, open postacert.eml. In Mail, Outlook or Thunderbird a double-click, or a drag into the mail program, shows the inner message.
3. Among the inner attachments, look for the document file, for example determina.pdf.p7m or fattura.xml.p7m.
4. Save it in a matter folder, without renaming it and without removing .p7m.

Some webmail views already show the original message attachments and hide the complexity. Others show only the three technical files. If you do not see the .p7m, it is not necessarily missing. It is still inside postacert.eml.

On a phone, double-clicking .eml is often useless. Open the provider’s webmail in Safari or Chrome, which usually lists the attachments in the clear, and save the .p7m. The reading path is in Open a P7M on Android and iPhone. On iPhone, do not count on the Share menu toward the reader.

Open only that file

With the .p7m saved, open Lettore P7M and select it. You will see the content preview, if the format is supported, and the checks on the sender’s signature: integrity, the certificate, the available chain and revocation. The document is not sent to a server in order to be read.

If the attachment is a .pdf.p7m, the preview is the PDF. If it is a FatturaPA .xml.p7m, the view is the readable invoice. If it is another format, there may be no preview. The extracted content remains the way to open it in the right program. If an error appears, the steps are in A P7M file will not open.

Two signatures sit together and do not replace each other.

Signature	Who applies it	What it concerns
smime.p7s	The PEC provider	Transport of the message
The .p7m attachment	The sender, if they signed the file	The document content

A PDF without .p7m, sent by PEC, has channel certification if the PEC message is intact. It does not, for that fact alone, have the sender’s digital signature on the file. PEC does not turn an ordinary attachment into a signed document.

Receipts, copies and the archive

A sender receives an acceptance receipt and, if delivery succeeds, a delivery receipt. Those receipts can also contain a daticert.xml and a pointer to the message. Keep the original message and the receipts together. They are the trace of sending. They do not replace the signed attachment, and the signed attachment does not replace the receipts.

For the archive, keep:

• the complete message, as .eml, if the client lets you save it;
• the receipts, if you are the sender;
• the original .p7m attachment, in a matter folder;
• a reading copy only if you need one, produced as described in Extract a PDF from a P7M file, and never in place of the envelope.

A .p7m of a few kilobytes, in a message that should contain a filing, deserves a suspicious look. It may be a receipt or an empty file. Compare subject and size with what you expect before you archive it as “the filing”.

Personal data and office habits

PEC attachments often contain tax codes, financial data or health data. Saving them in a shared mailbox or forwarding them to a personal address widens the set of people who can read them. Define, in the office, who downloads, into which folder, and who may export copies.

The reader processes the file on the device. That removes one upload step. It does not exhaust the office’s duties. Do not send the .p7m to the site’s support address: the contact form asks you to describe the problem without confidential documents.

If the filing arrives for a court deposit or for a notice between lawyers, reading is only the first gesture. The rules of the file are in P7M files in Italian court filings.

Example: four attachments, one filing

Webmail shows a message “Notificazione ai sensi di legge” with four rows: postacert.eml (40 KB), daticert.xml (3 KB), smime.p7s (8 KB) and, only after you open postacert.eml, comparsa.pdf.p7m (240 KB). The first three are not the brief. The fourth is, if the preview really shows that filing and not an empty cover.

Save comparsa.pdf.p7m in the matter folder. Open the reader and check the signer. Then also save the message .eml, if the client allows it, in a pec subfolder. Do not rename smime.p7s to .p7m to “try it”. It is a different object. Do not open daticert.xml in an invoice reader expecting the filing. That XML certifies the message.

If a colleague forwards only the extracted PDF, you lack both the envelope and the PEC message. Ask for the .p7m and, if you need proof of delivery, the message or the receipts. The reading copy can travel in the same internal mail, provided its name is not identical to the envelope. Two files both called comparsa.pdf in Downloads are the most common way to upload the wrong one later.

Frequently asked questions

Is smime.p7s the signed document?

No. It is the PEC provider’s signature on the transport envelope. The sender’s document, if there is one, is the .p7m attachment inside the original message.

What is daticert.xml for?

It contains the message certification data, such as sender, recipient, date and identifier. It does not contain the contract or the invoice.

Does the reader open the whole PEC message?

No. It opens the .p7m file you select. It does not read postacert.eml on its own and it does not verify the provider’s signature on the transport envelope.

Does forwarding PEC to ordinary mail erase the attachment signature?

The forwarded message is no longer PEC. The .p7m attachment, if it arrives intact, remains a signed envelope and can be opened like any other P7M.

A check before you forward the copy

Open the right .p7m, read the signer, and only then create a reading copy for a colleague. If the certificate is expired or revoked, do not hide the result in the forwarding mail. Say that the check should be read in Expired or revoked signature and keep the envelope. PEC certifies the channel. The attachment signature, if present, concerns the content. You need both, and they are not the same file.