Integrations
Connect Billnado to Billtobox via Mailbox
Configure the Billtobox purchase and sales addresses in Billnado, authorise the export senders and check onward delivery to customers.
Updated on October 22, 2026
Mailbox delivers invoices and credit notes from Billnado to your Billtobox account. You need access to the Billnado administration and the receiving settings for the same business in Billtobox. Purchases and sales have separate import settings.
Step 1: copy the address for purchase documents
In Billtobox, open the incoming email settings (Instellingen > Inkomend > Via e-mail in the Dutch interface). Copy your business’s unique receiving address for purchase documents. Use an existing account address; you do not need to create a new address for the Billnado connection.
The Billtobox help on incoming invoices by email explains where to find the addresses. Ask your accountant to confirm how purchase credit notes are processed at the same address.
Step 2: check sales import and authorised senders
Open the outgoing settings in Billtobox (Instellingen > Uitgaand in Dutch). The email addresses section (E-mailadressen) lists the sales invoice import addresses.
Billtobox supports importing from an authorised sender. Its option to automatically accept documents from specified email addresses determines which senders may submit sales documents. Ask the account administrator to add the actual Billnado export senders; Billnado support can confirm these. Allow for a separate sender for sales credit notes as well.
Use this authorisation method for the connection. Billtobox’s alternative import method uses a unique key in the subject; you cannot enter this key in Billnado’s Mailbox settings. The Billtobox guide to importing sales invoices by email describes both options.
Note: Billtobox can automatically send imported sales XML to the customer. Ask your accountant to check the sales invoice settings before connecting so that an invoice already sent from Billnado is not delivered again.
Step 3: enter the destinations in Billnado and save
In the correct Billnado administration, open Settings > Integrations > Accounting. Select Mailbox under Accounting software.
| Billnado fields, for both PDF and UBL | Billtobox destination |
|---|---|
| Email for sales invoices | Use the sales import address in the outgoing settings, with the Billnado sender authorised. |
| Email for sales credit notes | Use the sales credit note destination confirmed by your accountant, with the corresponding sender authorised. |
| Email for purchase invoices | Use the unique address in the incoming email settings. |
| Email for purchase credit notes | Use the purchase credit note destination confirmed by your accountant. |
Complete every PDF and UBL field with the destination for that document type. Billnado sends one file per document, giving priority to a suitable UBL and otherwise sending the available PDF. Using the purchase address for sales documents does not replace sales import.
Set Deferral period for automatic export. Match Maximum attachment size to Billtobox’s receiving limits; Billnado defaults to 2 MB. Discuss Only send UBLs that are PEPPOL-compliant for your sales documents. Then check all addresses and choose Save.
Step 4: check receipt and onward delivery
Together with your accountant, choose a document not yet submitted. Check it using the eye icon in the Billnado document list and choose Export. This actually sends it to Billtobox.
Check the incoming or outgoing section of Billtobox, depending on the document. Compare its number, amount and invoice or credit note classification. For sales, also check that the import follows the agreed processing and does not unintentionally cause another delivery to your customer.
Daily use and troubleshooting
If sales import is rejected, first check the sales address and authorised Billnado sender. For missing purchase documents, check receipt in the incoming section and any filter tasks. Also check format and file size limits before exporting again.
Mailbox does not send postings, corrections or payment statuses from Billtobox back to Billnado. To disable future automatic exports, select None under Accounting software and save. This does not delete documents from Billtobox.