Hi Tobias, I actually published a blog post about that last month: https://redsift.com/blog/ed25519-dkim-support-weak-keys
Happy to answer any questions! -Faisal On Monday, May 18th, 2026 at 6:33 PM, Tobias Fiebig via mailop <[email protected]> wrote: > Moin, > > fyi, i am currently debugging some deliverability issues with > outlook.com (mails queued, but seem to not be delivered). > > After getting my hands on an EML, i saw that the messages get > quarrantined, and show for a DKIM failure. > > The messages are triple-signed (SHA1, SHA256, ED25519). The former two > validate correctly, but the latter signature results in a: > > header.d=acsac.org;dkim=fail (signature syntax error) > > Removing the ed25519 seems to help; Also, no indicators on the > dashboard > for the IPs, all in good standing, and can also deliver flawlessly > to all other ESPs. > > Are there similar experiences of reduced deliverability by senders > multi-signing, and including ed25519? > > With best regards, > Tobias > > -- > Univ.Prof. Dr.-Ing. Tobias Fiebig > T +31 616 80 98 99 > M [email protected] > _______________________________________________ > mailop mailing list > [email protected] > https://list.mailop.org/listinfo/mailop > _______________________________________________ mailop mailing list [email protected] https://list.mailop.org/listinfo/mailop
