So I was trying to enable Cyrillic support for sendmail in RockyLinux8 / AlmaLinux 8 and found that it is not supported by sendmail 8.15 .2 which is currently available for these systems as of May 2022. Only sendmail version 8.17.x is supporting EAI (Email Address Internationalization) / SMTPUTF8 standard, as defined in RFC 6531 (SMTPUTF8 extension), RFC 6532 (Internationalized email headers) and RFC 6533 (Internationalized delivery status notifications).
Since Postfix is supporting this from 2014, it is time for every sendmail to have SMTPUTF8 support, but sendmail was apparently late to the game and it is still important to have it included, since even if you dont have any destination UTF8 e-mails on your servers, it is still important for your users to be able to send e-mails to UTF8 aware servers.
Since RHEL8 /CentOS8 came out few years ago – sendmail version included by default dont have UTF8 support.
So even in RHEL9 /CentOS 9 Stream, sendmail included is 8.16 – still dont have support for it so i decided to make my own RPMs by adapting sendmail 8.17.1 from Fedora 35, which also dont have SMTPUTF8 enabled by default eventhough sendmail 8.17 fully supoort it. So i made my own rpms. I just added
APPENDDEF(\`confENVDEF',\`-DUSE_EAI') APPENDDEF(\`confLIBS', \`-licuuc')
to sendmail.spec from Fedora 35 sendmail 8.17.1 srpm and rebuilt it with
rpmbuild -ba ./sendmail.spec
On RockyLinux 8 and now we have
sendmail-8.17.1-1.el8.x86_64.rpm sendmail-debugsource-8.17.1-1.el8.x86_64.rpm sendmail-milter-debuginfo-8.17.1-1.el8.x86_64.rpm sendmail-cf-8.17.1-1.el8.noarch.rpm sendmail-doc-8.17.1-1.el8.noarch.rpm sendmail-milter-devel-8.17.1-1.el8.x86_64.rpm sendmail-debuginfo-8.17.1-1.el8.x86_64.rpm sendmail-milter-8.17.1-1.el8.x86_64.rpm
Which should be compatible with all *EL8 distros. To download, go here, and install it with
rpm -i sendmail-8.17.1-1.el8.x86_64.rpm
Install other packages as needed (mostly you will need sendmail-cf and sendmail-milter
If you need me to try to to compile it on other EL like distro feel free to contact me