Setting up your own mail server (SMTP)

With the delivery method "Own SMTP", Rechnungskit sends your invoices through your own mail server. The emails then come from your domain and land in your sent folder. The alternative is "Rechnungskit delivery", which works without any setup.

Setting it up

1. Open Settings → Email delivery and choose "Own SMTP" as the delivery method.
2. Enter host, port, user and password. For the host, only the server name, without https:// and without a path.
3. Click "Test connection". Rechnungskit logs in to your server and sends you a test email.

For security reasons you never see the password again after saving; the field then only shows "Saved". "Test connection" then uses the saved password. If you change the server or the user, Rechnungskit asks for the password again, so it never goes to a different server.

When you save, Rechnungskit logs in to your server right away, without a test email. Below the fields you then see whether the saved credentials work and when that was last checked. Every real invoice sent through your server keeps this display up to date too. If your server rejects the login, the reason appears there. 4. If the test succeeds, save the delivery method.

Good to know:

• The sender is the user. Invoices go out with the address you use to log in to the mail server. The user therefore has to be the mailbox you want to send from.
• Encryption is required. On port 587 Rechnungskit uses STARTTLS, on port 465 a direct TLS connection. Rechnungskit does not accept an unencrypted connection.
• The server must be reachable from the internet. A mail server that only runs inside the company network does not work.

Gmail and Google Workspace

Google does not allow logging in with the normal password to send mail from other programs. You need an app password:

1. In your Google account, under Security, turn on 2-Step Verification if it is still off.
2. Under Security → App passwords, create a new app password, for example named "Rechnungskit".
3. Enter the 16 characters in Rechnungskit as the password, without spaces.

With Google Workspace, the administrator can block app passwords or SMTP access for the mailbox. If the App passwords option does not show up, ask your domain's administrator.

Microsoft 365 and Outlook

"Authenticated SMTP" (SMTP AUTH) must be enabled for the mailbox. The administrator sets this in the Microsoft 365 admin center on the user under Mail, Manage email apps. Microsoft is gradually restricting password login for sending mail. If SMTP AUTH cannot be switched on for you, use Rechnungskit delivery.

Other providers

Hostname, port and type of login are in your provider's help pages, usually under "SMTP" or "outgoing mail server". Use port 587 or 465. Some providers also require a separate password for external programs.

Error messages and what they mean

If the test or a delivery fails, Rechnungskit shows what caused it, and for the test also your mail server's response.

Only the last row is on the customer's side. All other errors come from your mail server settings, and simply sending the invoice again does not help there.

When an invoice did not go out

The invoice itself has been created and archived in any case; only the delivery is missing. After fixing the problem, open the invoice and click "Send invoice" or "Send again". You then close the related task yourself.

Rechnungskit delivery as the alternative

If you switch to "Rechnungskit delivery" under Settings → Email delivery, invoices go out through Rechnungskit's infrastructure, with your company name as the sender name. Your customers' replies go to the reply-to address you enter there.