Confusing portage behavior attempting to install sendmail

[donallen]

I attempt to install sendmail:

sophie ~ # emerge sendmail
Calculating dependencies... done!
[ebuild N ] mail-filter/procmail-3.22-r7 USE="-mbox (-selinux)"
[ebuild N ] mail-mta/sendmail-8.14.0 USE="ipv6 ssl tcpd -ldap -mailwrapper -mbox -nis -sasl -sockets"
[blocks B ] mail-mta/ssmtp ("virtual/mta" is blocking mail-mta/sendmail-8.14.0, mail-mta/ssmtp-2.62-r3)

* Error: The above package list contains packages which cannot be
* installed at the same time on the same system.

For more information about Blocked Packages, please refer to the following
section of the Gentoo Linux x86 Handbook (architecture is irrelevant):

http://www.gentoo.org/doc/en/handbook/handbook-x86.xml?full=1#blocked

I then did

sophie ~ # equery list virtual/
[ Searching for all packages in 'virtual' among: ]
* installed packages
[I--] [ ] virtual/blas-1.0 (0)
[I--] [ ] virtual/editor-0 (0)
[I--] [ ] virtual/emacs-22 (0)
[I--] [ ] virtual/ghostscript-0 (0)
[I--] [ ] virtual/glu-7.0 (0)
[I--] [ ] virtual/glut-1.0 (0)
[I--] [ ] virtual/init-0 (0)
[I--] [ ] virtual/jdk-1.4.2 (1.4)
[I--] [ ] virtual/jdk-1.6.0 (1.6)
[I--] [ ] virtual/jre-1.6.0 (1.6)
[I--] [ ] virtual/latex-base-1.0 (0)
[I--] [ ] virtual/libiconv-0 (0)
[I--] [ ] virtual/libintl-0 (0)
[I--] [ ] virtual/opengl-7.0 (0)
[I--] [ ] virtual/pager-0 (0)
[I--] [ ] virtual/perl-Compress-Raw-Zlib-2.015 (0)
[I--] [ ] virtual/perl-Compress-Zlib-2.015 (0)
[I--] [ ] virtual/perl-Digest-MD5-2.36 (0)
[I--] [ ] virtual/perl-File-Spec-3.25 (0)
[I--] [ ] virtual/perl-IO-Compress-Base-2.015 (0)
[I--] [ ] virtual/perl-IO-Compress-Zlib-2.015 (0)
[I--] [ ] virtual/perl-MIME-Base64-3.07 (0)
[I--] [ ] virtual/perl-Scalar-List-Utils-1.19 (0)
[I--] [ ] virtual/perl-Storable-2.16 (0)
[I--] [ ] virtual/perl-Test-Simple-0.70 (0)
[I--] [ ] virtual/perl-libnet-1.21 (0)
[I--] [ ] virtual/postgresql-base-8.0 (8.0)
[I--] [ ] virtual/xft-7.0 (0)
sophie ~ #

No virtual/mta? Totally confused at this point, I did

sophie ~ # emerge ssmtp
Calculating dependencies... done!

>>> Verifying ebuild manifests

>>> Emerging (1 of 1) mail-mta/ssmtp-2.62-r3
* ssmtp_2.62.orig.tar.gz RMD160 SHA1 SHA256 size ... [ ok ]
* checking ebuild checksums ... [ ok ]
* checking auxfile checksums ... [ ok ]
....

which, to my utter surprise, worked. Gee, I thought the non-existent virtual/mta was blocking this.

I then did

sophie ~ # emerge sendmail
Calculating dependencies... done!
[ebuild N ] mail-filter/procmail-3.22-r7 USE="-mbox (-selinux)"
[ebuild N ] mail-mta/sendmail-8.14.0 USE="ipv6 ssl tcpd -ldap -mailwrapper -mbox -nis -sasl -sockets"
[blocks B ] mail-mta/ssmtp ("virtual/mta" is blocking mail-mta/sendmail-8.14.0, mail-mta/ssmtp-2.62-r3)

But

sophie ~ # equery list ssmtp
[ Searching for package 'ssmtp' in all categories among: ]
* installed packages
[I--] [ ] mail-mta/ssmtp-2.62-r3 (0)
sophie ~ #

So here's my question: the emerge sendmail appears to be telling me that it can't emerge mail-mta/ssmtp, which is already installed, because virtual/mta, which doesn't exist on my system, is blocking both sendmail and ssmtp???? Now perhaps the emerge of sendmail needs to emerge ssmtp whether already emerged or not because it needs to do some special configuring specific to sendmail?? That's just a guess, but the only explanation I can offer for that apparent anomaly. But the non-existent virtual/mta blocking both sendmail and ssmtp?? I'm stumped.

Can someone unconfuse me, please? And help me get sendmail installed? Thanks in advance.
_________________
/Don Allen

[Hu]

Near the end, the block message says you cannot install mail-mta/sendmail because you have mail-mta/ssmtp installed. The virtual/mta is created by a PROVIDE= line in both the mail-mta/sendmail and mail-mta/ssmtp ebuilds. Both of them block virtual/mta, though mail-mta/sendmail only blocks it if you have USE=-mailwrapper.

I have a system where mail-mta/sendmail was installed during setup with USE=-mailwrapper and had no problems. Looking at our differences, I think you may be getting burned by the dependency resolver. Since you have USE=-mbox, mail-mta/sendmail has a PDEPEND relation on mail-filter/procmail. However, mail-filter/procmail has a DEPEND relation on virtual/mta. I suspect, but do not know enough about Portage to confirm, that the dependency resolver becomes confused by this. Try doing: USE=mbox emerge mail-mta/sendmail && emerge --oneshot mail-filter/procmail && emerge mail-mta/sendmail. This will install mail-mta/sendmail with USE=mbox so that it does not have a dependency on mail-filter/procmail. It then installs mail-filter/procmail, which should install cleanly since an MTA is available. Finally, it reinstalls mail-mta/sendmail with your preferred USE flags. Alternately, you could shorten this to be: emerge --nodeps mail-mta/sendmail && emerge --oneshot mail-filter/procmail. I dislike suppressing dependency checks, though.

If this works, you should probably report a Portage bug, because I thought a PDEPEND would have let Portage defer installing mail-filter/procmail. If it had deferred installation, then this would not have happened.