Hi all, I’m wondering if I’m understanding this correctly and if so, if it is a good practice. In email mesases received from IONOS, I see in the header: X-Received: by 2002:ac8:5ac5:0:b0:46d:fd08:7c9f with SMTP id d75a77b69052e-46e12a462a7mr251941861cf.22.1737462364476; Tue, 21 Jan 2025 04:26:04 -0800 (PST) Another example: X-Received: by 2002:a05:622a:38b:b0:46c:7646:4a1e with SMTP id d75a77b69052e-46e12a62966mr243715391cf.13.1737416130721; Mon, 20 Jan 2025 15:35:30 -0800 (PST) It looks to me like they are using 2002 as the IPv6 address of the email for the client hosted mail/domains? Regards, Jordi @jordipalet ********************************************** IPv4 is over Are you ready for the new Internet ? http://www.theipv6company.com The IPv6 Company This electronic message contains information which may be privileged or confidential. The information is intended to be for the exclusive use of the individual(s) named above and further non-explicilty authorized disclosure, copying, distribution or use of the contents of this information, even if partially, including attached files, is strictly prohibited and will be considered a criminal offense. If you are not the intended recipient be aware that any disclosure, copying, distribution or use of the contents of this information, even if partially, including attached files, is strictly prohibited, will be considered a criminal offense, so you must reply to the original sender to inform about this communication and delete it.