The URL can be updated, if there is a new one, or set to https://wiki.gentoo.org/wiki/No_homepage, if there is no homepage.
http://thewalter.net/stef/software/clamsmtp/ looks like the new HOMEPAGE. SRC_URI could also be changed to http://thewalter.net/stef/software/${PN}/${P}.tar.gz
If this is really the correct repository, we can also add <changelog>http://thewalter.net/stef/software/clamsmtp/ChangeLog</changelog> to metadata. https://devmanual.gentoo.org/ebuild-writing/misc-files/metadata/
PR with fix in https://patch-diff.githubusercontent.com/raw/gentoo/gentoo/pull/3118.patch or https://patch-diff.githubusercontent.com/raw/gentoo/gentoo/pull/3118
err, last link fail, https://github.com/gentoo/gentoo/pull/3118
commit 03da1af08e093dd949ea71b280e86bc45ff61408 (HEAD) Author: Wim Muskee <wimmuskee@gmail.com> AuthorDate: Wed Dec 14 19:57:46 2016 +0100 Commit: Patrice Clement <monsieurp@gentoo.org> CommitDate: Sat Dec 17 23:05:24 2016 +0100 mail-filter/clamsmtp: update SRC_URI and HOMEPAGE. Gentoo-Bug: https://bugs.gentoo.org/586738 Closes: https://github.com/gentoo/gentoo/pull/3118 Signed-off-by: Patrice Clement <monsieurp@gentoo.org> mail-filter/clamsmtp/clamsmtp-1.10.ebuild | 10 +++++----- mail-filter/clamsmtp/metadata.xml | 3 +++ 2 files changed, 8 insertions(+), 5 deletions(-) PR merged, thanks!