diff --git a/mail-mta/sendmail/Manifest b/mail-mta/sendmail/Manifest
index fd5276aadc0f..1971a45519aa 100644
--- a/mail-mta/sendmail/Manifest
+++ b/mail-mta/sendmail/Manifest
@@ -3,5 +3,7 @@ DIST sendmail.8.18.1.10.tar.gz 2367668 BLAKE2B 22fe4f3484c3f888b909bebe3ad0dd3d6
 DIST sendmail.8.18.1.10.tar.gz.sig 543 BLAKE2B 14bbd896f3fb89422cc999e817b9e859058295102a30da319de89f05fb96acd15424aa00694fcb6aa29fdaad909ffa47fb20f387946f77c6a6cc9fb5c4966bf9 SHA512 469bb57b1b75c08fbb9aba597637ac9d27204cbad58e46cfc30807932f4d7428216e096fca4ad91bd5719aaffcd04b0aafe56979b4d84b957a8fa88033f833ce
 DIST sendmail.8.18.1.15.tar.gz 2371839 BLAKE2B f08ebd245f23f2a02380251d241829417d53c550089ed551c8239d1e6d20f797fbb836a7bb48b5cf21f02fc8d499b831531fa3094d77266338a81a1e2b99efe8 SHA512 09587e28213e1d50806271b85de4b4ca3e6ed0b95a12a466fcdf1a6bd1973acd43ab2c8504420f1df786538ad2b8bbd79f13e89bd6177df83cb59606caaf5fca
 DIST sendmail.8.18.1.15.tar.gz.sig 543 BLAKE2B b83ebff2df2fa6a86102a39708b82617661ec0d23458ef594a67b706876427307f9d1240309705c1ab6e6acc6c8aa5d05e22397a99cda695172c16fb8bb9a266 SHA512 a5dec294248a1c0f63a740534026ac150bb98e23aad68d05ffff4725083667855dfd58f724ba90a9cc6a2e089c75a07e18ad82c0c9efb9e08c7b3e6ea63bbf7d
+DIST sendmail.8.18.1.16.tar.gz 2372700 BLAKE2B 0e0482111fce96d7885c226203648ca0e7a019a85e729f5dd71dc1b6036071cdbeacc0931dd5b83872c59f15fc46c7c68f97ba248884a12c9ea228e5d74f461a SHA512 92683ce741cf7da6b92cef95209f021641971466709fe5474dcbce04089b1631d54399d0f9414b9c083ea5b918db8418a90fee279b6084cd4961c27bc6389812
+DIST sendmail.8.18.1.16.tar.gz.sig 543 BLAKE2B 3d97b0344dca35c7950259c370fd37e06fd8a4d3e2894df1058ef9ef735c142f6e71161d1bba598fac5ccb52641eaf4f97b45b35c87c9e37ffebe043c16861a9 SHA512 067926cec5377bfa37af81cee8138c59d7f64326558eb849b926103cda4c1cf6d75cac3962dcea3fcf92c1f2cb68079b72d13028c32c1306fadf60a9acdcf612
 DIST sendmail.8.18.1.tar.gz 2401566 BLAKE2B 3afa36073fd611c7fdb43ef0ab9f02d5fb8ae388e9471bdc7275c6c9dcee0a654f46ddef505b70e978cb1b818b0da375250678e501676d8bace534d59ee40d90 SHA512 9ce713b44439d4de6faa9e3cdfa2226b44b4fbeb352a5f81584c062570e9472da244158287e489aabe258d28fe54ca4964565c7b0adc7e1763d212be42f98061
 DIST sendmail.8.18.1.tar.gz.sig 543 BLAKE2B f5f8ffaee2b4380babb033257aa30a3ade3686f3ae3dc4ced3beb25698c1917489e05456cf6b3cfcf3f0a8a1725ac42a6ce1db317939f944012e994672f6c22d SHA512 a1b3fc2278061c220ca36b954e333867a187b52c32ecd10793a12c1c90c0466bc3f1e6f76ca3aeaaf02e14f71f8cef418f5291557461b61509ed255c55c6ef47
diff --git a/mail-mta/sendmail/sendmail-8.18.1.16.ebuild b/mail-mta/sendmail/sendmail-8.18.1.16.ebuild
new file mode 100644
index 000000000000..ba15b5762f48
--- /dev/null
+++ b/mail-mta/sendmail/sendmail-8.18.1.16.ebuild
@@ -0,0 +1,316 @@
+# Copyright 1999-2025 Gentoo Authors
+# Distributed under the terms of the GNU General Public License v2
+
+EAPI=8
+
+# Note: please bump this together with mail-filter/libmilter and app-shells/smrsh
+
+VERIFY_SIG_OPENPGP_KEY_PATH="/usr/share/openpgp-keys/sendmail.asc"
+inherit systemd toolchain-funcs verify-sig
+
+DESCRIPTION="Widely-used Mail Transport Agent (MTA)"
+HOMEPAGE="https://www.sendmail.org/"
+if [[ -n $(ver_cut 4) ]] ; then
+	# Snapshots have an extra version component (e.g. 8.17.1 vs 8.17.1.9)
+	SRC_URI="
+		https://ftp.sendmail.org/snapshots/${PN}.${PV}.tar.gz
+		verify-sig? ( https://ftp.sendmail.org/snapshots/${PN}.${PV}.tar.gz.sig )
+	"
+fi
+
+SRC_URI+="
+	https://ftp.sendmail.org/${PN}.${PV}.tar.gz
+	verify-sig? ( https://ftp.sendmail.org/${PN}.${PV}.tar.gz.sig )
+"
+SRC_URI+="
+	https://ftp.sendmail.org/past-releases/${PN}.${PV}.tar.gz
+	verify-sig? ( https://ftp.sendmail.org/past-releases/${PN}.${PV}.tar.gz.sig )
+"
+
+LICENSE="Sendmail GPL-2" # GPL-2 is here for initscript
+SLOT="0"
+KEYWORDS="~alpha ~amd64 ~arm ~arm64 ~hppa ~mips ~ppc ~ppc64 ~riscv ~s390 ~sparc ~x86"
+IUSE="+berkdb eai fips ldap mbox nis sasl selinux ssl tcpd tinycdb"
+REQUIRED_USE="
+	|| ( berkdb tinycdb )
+	fips? ( ssl )
+"
+
+DEPEND="
+	acct-group/smmsp
+	>=acct-user/smmsp-0-r2
+	net-mail/mailbase
+	berkdb? ( >=sys-libs/db-3.2:= )
+	eai? ( dev-libs/icu:= )
+	elibc_musl? ( virtual/libcrypt:= )
+	ldap? ( net-nds/openldap:= )
+	nis? ( net-libs/libnsl:= )
+	sasl? ( >=dev-libs/cyrus-sasl-2.1.10 )
+	ssl? (
+		>=dev-libs/openssl-1.1.1:=
+		fips? ( >=dev-libs/openssl-3:=[fips] )
+	)
+	tcpd? ( sys-apps/tcp-wrappers )
+	tinycdb? ( dev-db/tinycdb )
+"
+RDEPEND="
+	${DEPEND}
+	>=mail-filter/libmilter-1.0.2_p2
+	sys-devel/m4
+	!mail-mta/courier
+	!mail-mta/esmtp
+	!mail-mta/exim
+	!mail-mta/msmtp[mta]
+	!mail-mta/netqmail
+	!mail-mta/notqmail
+	!mail-mta/nullmailer
+	!mail-mta/opensmtpd
+	!mail-mta/postfix
+	!>=mail-mta/ssmtp-2.64-r2[mta]
+	selinux? ( sec-policy/selinux-sendmail )
+"
+BDEPEND="
+	sys-devel/m4
+	virtual/pkgconfig
+	verify-sig? ( ~sec-keys/openpgp-keys-sendmail-20250220 )
+"
+PDEPEND="
+	!mbox? (
+		|| (
+			mail-filter/procmail
+			mail-filter/maildrop
+		)
+	)
+"
+PATCHES=(
+	"${FILESDIR}"/${PN}-8.13.1-delivered_hdr.patch
+	"${FILESDIR}"/${PN}-8.16.1-build-system.patch
+)
+
+src_prepare() {
+	default
+
+	local confCCOPTS="${CFLAGS}"
+	local confENVDEF="-DMAXDAEMONS=64 -DHAS_GETHOSTBYNAME2=1"
+	local confLDOPTS="${LDFLAGS}"
+	local confLIBS=
+	local confMAPDEF="-DMAP_REGEX"
+	local conf_sendmail_LIBS=
+
+	# Always enable ipv6 and sockets
+	confENVDEF+=" -DNETINET6 -DSOCKETMAP"
+
+	# Enable experimental features
+	confENVDEV+=" -D_FFR_SAMEDOMAIN -D_FFR_MF_ONEDOMAIN"
+
+	if use berkdb; then
+		# See bug #808954 for FLOCK
+		confENVDEF+=" -DHASFLOCK=1"
+		confMAPDEF+=" -DNEWDB"
+		confLIBS+=" -ldb"
+	else
+		confMAPDEF+=" -UNEWDB"
+	fi
+
+	if use eai; then
+		confCCOPTS+=" $($(tc-getPKG_CONFIG) --cflags icu-uc)"
+		confENVDEF+=" -DUSE_EAI"
+		confLIBS+=" $($(tc-getPKG_CONFIG) --libs icu-uc)"
+	fi
+
+	if use ldap; then
+		confMAPDEF+=" -DLDAPMAP"
+		confLIBS+=" -lldap -llber"
+	fi
+
+	use nis && confENVDEF+=" -DNIS"
+
+	if use sasl; then
+		confCCOPTS+=" $($(tc-getPKG_CONFIG) --cflags libsasl2)"
+		confENVDEF+=" -DSASL=2"
+		conf_sendmail_LIBS+=" $($(tc-getPKG_CONFIG) --libs libsasl2)"
+	fi
+
+	if use ssl; then
+		# Bug #542370 - lets add support for modern crypto (PFS)
+		confCCOPTS+=" $($(tc-getPKG_CONFIG) --cflags openssl)"
+		confENVDEF+=" -DSTARTTLS -D_FFR_DEAL_WITH_ERROR_SSL"
+		confENVDEF+=" -D_FFR_TLS_1 -D_FFR_TLS_EC"
+		# Bug #944822 - fix certification chain with intermediate cert file
+		confENVDEF+=" -D_FFR_TLS_USE_CERTIFICATE_CHAIN_FILE"
+		confENVDEF+=" -DDANE"
+
+		if use fips; then
+			confENVDEF+=" -D_FFR_FIPSMODE"
+		fi
+
+		conf_sendmail_LIBS+=" $($(tc-getPKG_CONFIG) --libs openssl)"
+	fi
+
+	if use tcpd; then
+		confENVDEF+=" -DTCPWRAPPERS"
+		confLIBS+=" -lwrap"
+	fi
+
+	if use tinycdb; then
+		confMAPDEF+=" -DCDB=2"
+		confLIBS+=" -lcdb"
+	else
+		confMAPDEF+=" -UCDB"
+	fi
+
+	if use elibc_musl; then
+		confENVDEF+=" -DHASSTRERROR -DHASRRESVPORT=0 -DNEEDSGETIPNODE"
+
+		eapply "${FILESDIR}"/${PN}-musl-stack-size.patch
+		eapply "${FILESDIR}"/${PN}-musl-disable-cdefs.patch
+	fi
+
+	sed -e "s|@@confCC@@|$(tc-getCC)|" \
+		-e "s|@@confCCOPTS@@|${confCCOPTS}|" \
+		-e "s|@@confENVDEF@@|${confENVDEF}|" \
+		-e "s|@@confLDOPTS@@|${confLDOPTS}|" \
+		-e "s|@@confLIBS@@|${confLIBS}|" \
+		-e "s|@@confMAPDEF@@|${confMAPDEF}|" \
+		-e "s|@@conf_sendmail_LIBS@@|${conf_sendmail_LIBS}|" \
+		"${FILESDIR}"/site.config.m4 > devtools/Site/site.config.m4 \
+		|| die "failed to generate site.config.m4"
+
+	echo "APPENDDEF(\`confLIBDIRS', \`-L${EPREFIX}/usr/$(get_libdir)')" \
+		>> devtools/Site/site.config.m4 || die "failed adding to site.config.m4"
+}
+
+src_compile() {
+	sh Build AR="$(tc-getAR)" RANLIB="$(tc-getRANLIB)" || die "compilation failed in main build script"
+}
+
+src_install() {
+	dodir /usr/{bin,$(get_libdir)}
+	dodir /usr/share/man/man{1,5,8} /usr/sbin /usr/share/sendmail-cf
+	dodir /var/spool/{mqueue,clientmqueue} /etc/conf.d
+
+	keepdir /var/spool/{clientmqueue,mqueue}
+
+	local emakeargs=(
+		DESTDIR="${D}" LIBDIR="/usr/$(get_libdir)"
+		MANROOT=/usr/share/man/man
+		SBINOWN=root SBINGRP=root UBINOWN=root UBINGRP=root
+		MANOWN=root MANGRP=root INCOWN=root INCGRP=root
+		LIBOWN=root LIBGRP=root GBINOWN=root GBINGRP=root
+		MSPQOWN=root CFOWN=root CFGRP=root
+	)
+
+	local dir
+	for dir in libsmutil sendmail mailstats praliases smrsh makemap vacation editmap; do
+		emake -j1 -C obj.*/${dir} "${emakeargs[@]}" install
+	done
+	for dir in rmail mail.local; do
+		emake -j1 -C obj.*/${dir} "${emakeargs[@]}" force-install
+	done
+
+	fowners root:smmsp /usr/sbin/sendmail
+	fperms 2555 /usr/sbin/sendmail
+	fowners smmsp:smmsp /var/spool/clientmqueue
+	fperms 770 /var/spool/clientmqueue
+	fperms 700 /var/spool/mqueue
+	dodoc FAQ KNOWNBUGS README RELEASE_NOTES doc/op/op.ps SNAPSHOT_NOTES
+
+	dodoc sendmail/{SECURITY,TUNING}
+	newdoc sendmail/README README.sendmail
+	newdoc smrsh/README README.smrsh
+
+	newdoc cf/README README.cf
+	newdoc cf/cf/README README.install-cf
+
+	dodoc -r contrib
+
+	cp -pPR cf/. "${ED}"/usr/share/sendmail-cf || die
+
+	insinto /etc/mail
+	if use mbox; then
+		newins "${FILESDIR}"/sendmail.mc-r1 sendmail.mc
+	else
+		newins "${FILESDIR}"/sendmail-maildir.mc sendmail.mc
+	fi
+
+	# See discussion on bug #730890
+	m4 "${ED}"/usr/share/sendmail-cf/m4/cf.m4 \
+		<(grep -v "${EPREFIX}"/usr/share/sendmail-cf/m4/cf.m4 "${ED}"/etc/mail/sendmail.mc) \
+		> "${ED}"/etc/mail/sendmail.cf || die "cf.m4 failed"
+
+	echo "include(\`/usr/share/sendmail-cf/m4/cf.m4')dnl" \
+		> "${ED}"/etc/mail/submit.mc || die "submit.mc echo failed"
+
+	cat "${ED}"/usr/share/sendmail-cf/cf/submit.mc \
+		>> "${ED}"/etc/mail/submit.mc || die "submit.mc cat failed"
+
+	echo "# local-host-names - include all aliases for your machine here" \
+		> "${ED}"/etc/mail/local-host-names || die "local-host-names echo failed"
+
+	cat <<- EOF > "${ED}"/etc/mail/trusted-users || die "trusted-users cat failed"
+		# trusted-users - users that can send mail as others without a warning
+		# apache, mailman, majordomo, uucp are good candidates
+	EOF
+
+	cat <<- EOF > "${ED}"/etc/mail/access || die "access cat failed"
+		# Check the ${EPREFIX}/usr/share/sendmail-cf/README file for a description
+		# of the format of this file. (search for access_db in that file)
+		#
+
+	EOF
+
+	cat <<- EOF > "${ED}"/etc/conf.d/sendmail || die "sendmail cat failed"
+		# Config file for /etc/init.d/sendmail
+		# add start-up options here
+		SENDMAIL_OPTS="-bd -q30m -L sm-mta" # default daemon mode
+		CLIENTMQUEUE_OPTS="-Ac -q30m -L sm-cm" # clientmqueue
+		KILL_OPTS="" # add -9/-15/your favorite evil SIG level here
+
+	EOF
+
+	if use sasl; then
+		dodir /etc/sasl2
+		cat <<- EOF > "${ED}"/etc/sasl2/Sendmail.conf || die "Sendmail.conf cat failed"
+			pwcheck_method: saslauthd
+			mech_list: PLAIN LOGIN
+
+		EOF
+	fi
+
+	doinitd "${FILESDIR}"/sendmail
+	systemd_dounit "${FILESDIR}"/sendmail.service
+	systemd_dounit "${FILESDIR}"/sm-client.service
+}
+
+pkg_postinst() {
+	if ! use berkdb; then
+		ewarn "If your configuration relies on userdb, you should install"
+		ewarn "this package with USE=berkdb."
+	fi
+
+	if ! use mbox; then
+		elog "Starting with mail-mta/sendmail-8.18.1 you could use either"
+		elog "procmail or maildrop to use maildir-style mailbox in user's home directory."
+		elog ""
+		elog "If you prefer procmail (default), emerge mail-filter/procmail with USE=-mbox"
+		elog "and include the following lines in sendmail.mc to create your sendmail.cf"
+		elog "configuration file:"
+		elog "\tFEATURE(\`local_procmail')dnl"
+		elog "\tMAILER(\`procmail')dnl"
+		elog ""
+		elog "If you prefer maildrop, you'll need to ensure that you configure a mail"
+		elog "storage location using DEFAULT in /etc/maildroprc, for example:"
+		elog "\tDEFAULT=\$HOME/.maildir"
+		elog ""
+		elog "and include the following line in sendmail.mc to create your sendmail.cf"
+		elog "configuration file:"
+		elog "\tFEATURE(\`local_procmail',\`/usr/bin/maildrop',\`maildrop -d $u')dnl"
+	fi
+
+	ewarn "This version has enabled experimental code. Please read the file"
+	ewarn ""
+	ewarn "\t${EPREFIX}/usr/share/doc/${PF}/SNAPSHOT_NOTES"
+	ewarn ""
+	ewarn "for enable testing, provide feedback and report potential problems"
+	ewarn "directly to upstream."
+}