That's the standard wording in a Nabble email footer. Unfortunately, it's not always true.
In part it can depend on what macros the forum owner has edited, but in the case of a mail list archive it can also depend on the security measures taken by the list owner rather than archive owner.
If you search Nabble Support you will find that some mail lists reject Nabble emails because of DMARC issues. I'm not an expert on some of this stuff, but it will help Nabble if you can report the URL of the archive so they can investigate further.
Volunteer Helper - but recommending that users move off the platform!
Once the admin for GregHelp now deleted.