Why do the spam filters of Gmail and Hotmail block your newsletter?
Does your newsletter arrive properly at most providers, while ending up in the spam folder or being rejected altogether at Gmail and Hotmail addresses? This is because Google (Gmail) and Microsoft (Hotmail, Outlook and Live) have imposed stricter requirements on bulk email since 2024. These requirements were tightened further in May 2025.
For general information about spam filters, read why your newsletter ends up in the spam folder.
Gmail and Microsoft requirements
The requirements of both parties are very similar and focus on authentication, one-click unsubscribing and the number of spam complaints:
You do not need to do anything yourself for one-click unsubscribing: Laposta automatically includes the List-Unsubscribe header in every delivery.
Since June 2025, Gmail also shows users an overview of all their subscriptions, where they can unsubscribe with a single click without opening your newsletter. This makes a clean list even more important than before.
What you see in your list
In your list, you will notice that a higher percentage of Gmail and Hotmail addresses result in a bounce. If Gmail or Hotmail rejects your email, this causes a hard bounce and the subscriber is cleaned immediately: they are moved to the ‘cleaned’ tab in your subscriber overview and you can no longer email them. Click on ‘Details’ for such a subscriber to see the reason given by the receiving server. For Gmail, it might say rejected due to unauthenticated email, and for Hotmail sender not authorized. You can read about what happens to that address next under the global blocklist.
This mainly occurs if you send from a domain without configured authentication, or from a shared domain such as a free email address or an address from an internet service provider such as KPN.
What you can do yourself
Two measures are the most effective, with the first being by far the most important:
- Use a sender address on your own domain (for example
newsletter@example.com). Have your domain host or your IT department configure authentication and then activate this in your Laposta account. - Keep your list clean. Only send to people who have genuinely subscribed and remove inactive subscribers as much as possible.
You cannot bypass the spam filters of Gmail and Hotmail with formatting or subject line tricks, and you will not prevent spam complaints as long as you keep emailing people who no longer want your newsletter. Whether your newsletter lands in the inbox is never guaranteed, as the recipient and their provider ultimately decide this themselves. However, if you meet the requirements above, you have a good chance that your newsletter will also reach the inbox at Gmail and Hotmail.