Yes. A range of spam-detection tests is run on incoming mail and each message is assigned a spam score. Messages with spam scores higher than a threshold (currently set to 7) are rejected by our SMTP servers. The sending server is then responsible for generating a bounce message and delivering it to the sender. This ensures that:
Any legitimate message that is rejected by our mail servers will be bounced back to the sender and they will know that the message was not delivered due to anti-spam measures. They can then try re-sending the message, using an alternate address, etc.
Spam messages that are rejected by our servers will never generate "backscatter spam" which is when a bounce message is generated by the receiving mail server based on the "From:" address in the email message, which can easily be faked, rather than by the sending server (which, if it's a spam server will not actually bother to generate bounces to the fake sender address it's using). This ensures our servers don't contribute to the spam problem, the way so many other email servers sadly seem to.
Our servers don't waste resources processing and delivering messages that are almost definitely spam, and as a customer you simply don't even see the vast majority of spam that is targeted to your email addresses.
No message ever disappears mysteriously into a Junk folder, the way they do on GMail and other major email services, where the sender thinks the message was delivered, but the recipient doesn't see it because the email provider decided to silently put it in the Junk folder. We believe this is a horrible practice and is even a form of censorship and any email service that does this is fundamentally broken. Neomailbox accounts are completely free of this! Either a message is delivered to your Inbox, or it is rejected and the sender is informed. There is no 3rd option.
When messages are accepted for delivery, the spam score assigned to them is inserted into the header "X-SA-Score". You can use this header in email programs to filter messages into a Junk folder yourself, if you find that an even lower threshold works for you and you don't mind clearing out the Junk folder once in a while. However this is entirely optional and completely up to you. Our servers will still eliminate over 95% of the spam targeted at your mailbox even if you don't configure any further filtering yourself.
You can also use the disposable subdomain email addresses included with every Neomailbox Secure Email account to further control your email address privacy and minimise spam. You can use any address @yoursubdomain.neomailbox.ch (or @yoursubdomain.neomailbox.net) to send and receive mail. So you can use a unique disposable email address for each different purpose, and you can disable and re-enable any subdomain address from your Control Panel at any time. If you use Neomailbox with your Custom Domain Mail Hosting for your own domain name, you can also use unlimited disposable addresses @yourdomain in the same way.
We are also working on providing more individualised control over ant-spam options and more anti-spam mechanisms in the near future.