Squirrelmail (PHP app) should not be confused with Squirrel webmail (CGI app) distributed together with courier MTA package (bugs #84288, #229465) or even as a split package sqwebmail (bug #89980, will attach an ebuild to it soon).
Created attachment 198136 [details, diff] squirrelmail-1.4.19.ebuild.patch
commit d229371435c05ea46d79bd2172c69887888e9634 Author: Michał Górny <mgorny@gentoo.org> AuthorDate: Sat Jul 1 11:09:49 2017 Commit: Michał Górny <mgorny@gentoo.org> CommitDate: Sat Jul 1 11:19:48 2017 mail-client/squirrelmail: Remove last-rited pkg, #611422