How it works
One-time setup — enter login credentials
In company settings, enter your Data Mailbox ID and login password or certificate. Credentials are immediately encrypted with AES-256. Claudyx connects to ISDS, verifies identity, and displays the mailbox owner name.
Auto-sync every 15 minutes
Claudyx regularly downloads new messages from ISDS, saves attachments to your vault (or your own AWS/Azure/SharePoint), and marks messages as delivered. You won't miss anything, even if you don't log into the app.
Read, reply, archive
Received messages appear in a clean inbox. Each message can be opened, attachments viewed, receipt printed in HTML, or a ZFO downloaded for legal purposes. Sending PDZ — search for recipient, attach files, send.
Credit management and archiving
Current credit balance shown in the app; click to top up at kredit-ds.cz. Messages older than 90 days are automatically moved to archive — they remain searchable and are never lost.
What the module can do
Inbox
All received messages with attachments, read/unread status, and search.
Sent mail
Complete overview of sent PDZ with delivery status updated after sync.
90+ day archive
Messages older than 90 days are automatically archived — not lost, fully searchable.
HTML receipts + ZFO
Delivery date, pickup date, printable receipt, ZFO download for legal proceedings.
Send PDZ
Recipient lookup by IČO (Czech business ID) or name, attach files from vault or local.
Credit tracking
Real-time credit balance, transaction history, quick top-up link.
Per-user permissions
Three access levels — read, send, manage — independent of folder permissions.
Notifications
Email alert on new message arrival. Configurable per user.
Claudyx vs. specialized ISDS clients
| Feature | Claudyx | Mailproof | Mailo |
|---|---|---|---|
| ISDS management (inbox, sending) | |||
| ZFO delivery receipts | — | ||
| Attachments to company vault | — | — | |
| Document vault included | — | — | |
| Electronic signing included | — | — | |
| Document templates included | — | — | |
| Multiple mailboxes in one app | — | — | |
| Per-user permissions | — | — | |
| Full operation audit log | — | — | |
| Price | 2,990 CZK/company | 200–300 CZK | 390 CZK |
* Mailproof and Mailo are indicative prices. Claudyx includes vault, signing, and templates — ISDS is one of the modules.
Who benefits most from the ISDS module
Law firms and notaries
Communication with courts and authorities via Data Mailbox is a daily routine. Claudyx integrates it with the document archive.
Accountants and tax advisors
Manage ISDS for multiple clients in one environment — no switching between client logins.
Public sector and public bodies
ISDS as the primary communication channel. Claudyx connects it to the company document vault.
Frequently asked questions
What is the Czech Data Mailbox (ISDS)? +
The Czech Information System of Data Boxes (ISDS) is a government-mandated electronic communication channel for legal entities in the Czech Republic. All Czech companies and organizations with an IČO (business ID) are required to have a Data Mailbox for communication with government authorities (tax office, courts, social security, municipalities, etc.).
Do I need special software to access the Data Mailbox through Claudyx? +
No. Claudyx works entirely in the browser — no installation, no plugin. Log into Claudyx and the Data Mailbox is one of the tabs in the application.
How quickly are new messages synchronized? +
Automatic synchronization runs every 15 minutes. You can trigger a manual sync with a single click and new messages appear within seconds.
What is ZFO format and why do I need it? +
ZFO (Zaručená Forma Obrázku — Guaranteed Image Form) is an electronically signed delivery receipt for a message — the equivalent of a signed postal delivery notice. It has legal weight and is required as proof of delivery in court and administrative proceedings. Claudyx downloads and saves it automatically.
How much does sending a PDZ (paid data message) cost? +
PDZ pricing is set by the Czech Ministry of Interior and is currently 10 CZK per message. Payment comes from your ISDS credit, which can be topped up directly from Claudyx. Claudyx adds no surcharge for sending PDZ.
Can I have multiple Data Mailboxes in Claudyx (e.g., head office + branches)? +
Yes. In the PROFESSIONAL plan, one mailbox is included. Each additional mailbox can be added for 490 CZK/month. Each mailbox has its own permissions — different users can have access to different mailboxes.
How is the Data Mailbox login credential secured? +
The password (or certificate) for ISDS is stored encrypted using AES-256-GCM with a master key that is not part of the database. Even Claudyx administrators cannot see it in plain text.
Ready to get started?
30 days free, no credit card required. Full access to all features.