Why is your newsletter not arriving for recipients on the same domain?
Are you sending a newsletter to addresses on the same domain as your sender address, for example to colleagues at @myorganisation.co.uk? If so, that email may end up in their spam folder or be rejected, while subscribers outside your organisation receive the newsletter as usual.
Why your own email system blocks the newsletter
Your organisation’s email system expects emails from @myorganisation.co.uk to come from its own servers. Your newsletter comes from the outside, from Laposta’s servers. Some systems reject such a message. This results in a hard bounce, causing the address to be moved to the ‘cleaned’ tab. You can read what happens to that address next under the global blocklist. Other systems do accept the newsletter, but have it caught by a spam filter.
Fraud warning in Microsoft 365
With Microsoft 365 (formerly Office 365), these newsletters end up in the spam folder and are sometimes accompanied by a warning: ‘This sender failed our fraud detection checks and may be spoofed’. This message only appears for emails sent to your own domain, not for recipients outside your organisation.
Laposta has been in contact with Microsoft about this. The company acknowledges the issue, but does not have a solution for it. The only option within Microsoft 365 is to turn these checks off completely. This is not recommended, as this protection against phishing can be very useful. You can resolve this warning by authenticating your domain.
Checking whether your own domain is the cause and resolving it
If you want to be sure that the issue is caused by using the same domain, try sending the newsletter once from a sender address with a different domain. If it arrives as usual for your colleagues, then your own organisation’s email system is blocking the email.
If the newsletter also needs to arrive properly within your organisation, ask your system administrators to adjust this. Setting up domain authentication almost always helps: this allows the receiving party to see that the newsletter was sent on behalf of your own organisation and not by an unknown sender.