Email remains the most practical delivery channel for e-invoices. Here's why it works, how it compares to Peppol, and how to implement it.

When the topic of e-invoicing comes up, discussions often focus on Peppol access points and government portals. But for most B2B transactions, email is the simplest and most practical delivery channel for structured e-invoices — and it's fully compliant.

The Delivery Problem

Germany's e-invoicing mandate specifies the format (EN 16931 / XRechnung) but is flexible about the delivery channel. You can deliver a compliant e-invoice via:

Email — XML attachment or ZUGFeRD PDF
Peppol — the pan-European e-delivery network
Direct upload — to a government portal (ZRE/OZG for B2G)
EDI — traditional Electronic Data Interchange

For B2G (business-to-government), Peppol or direct portal upload is often required. But for B2B, there is no mandated delivery channel.

Why Email Works

Your recipients already have it

Every business has email infrastructure. No one needs to register for a Peppol access point, configure an AS4 endpoint, or integrate with a new portal. The invoice lands in the recipient's existing inbox.

It's auditable

Email provides a natural audit trail. Delivery status (delivered, bounced, deferred) is tracked at the SMTP level. Add DKIM signing and you get cryptographic proof of origin.

It supports both humans and machines

Send a ZUGFeRD PDF and the recipient can either:

Read it — open the PDF visually, just like a traditional invoice
Process it — extract the embedded XML for automated AP workflows

Or send a plain XML attachment alongside an HTML email body that summarizes the invoice for human review.

It's already how most invoices travel

The majority of B2B invoices in Germany are already sent via email — as PDF attachments. The transition to e-invoicing via email means changing the attachment format, not the delivery infrastructure.

Email vs. Peppol

Factor	Email	Peppol
Setup	None (existing infrastructure)	Register with access point provider
Cost	Included in email sending costs	Per-document fees from access point
Recipient coverage	Universal	Growing but not universal
B2G compliance	Depends on authority	Often required for federal invoices
Delivery confirmation	SMTP-level (delivered/bounced)	AS4 receipt at network level
Human readability	HTML body + attachment	XML only (needs viewer)

For most B2B use cases, email is the pragmatic choice. Peppol becomes relevant when trading partners specifically require it or for federal government invoicing.

Implementation with Postscale

Sending compliant e-invoices via email is a single API call:

curl -X POST https://api.postscale.io/v1/invoices/send \
  -H "Authorization: Bearer ps_live_..." \
  -H "Content-Type: application/json" \
  -d '{
    "from": "billing@yourdomain.com",
    "to": "ap@customer.de",
    "format": "xrechnung-ubl",
    "invoice": { ... }
  }'

Postscale handles:

XML generation — valid XRechnung from your JSON data
Validation — EN 16931 + XRechnung rules checked before sending
Email composition — professional HTML body + XML attachment
DKIM signing — cryptographic proof the invoice came from your domain
Delivery tracking — real-time status via webhooks

On the receiving side, Postscale's inbound processing automatically detects e-invoices in incoming email and extracts structured data for your webhook.

The Bottom Line

Don't over-engineer your e-invoicing delivery. Email is compliant, universal, and requires zero infrastructure changes for your recipients. Start with email delivery, and add Peppol later if specific trading partners require it.

Why Email is the Simplest E-Invoice Delivery Channel