bug#14271: 24.3; MAILHOST set in mail-source.el when using pop3.el

[Monte Stevens]

My MAILHOST environment variable is empty.

I start emacs with `emacsclient -ta "" foo'.

`M-x getenv MAILHOST' = ''

I start Gnus with `M-x gnus'; Gnus fetches mail from two pop servers as
defined in my .gnus.el file.

`M-x getenv MAILHOST' = 'pop.eastlink.ca'

pop servers definitions:

      mail-sources
      '(
        (pop
         :server "pop.eastlink.ca"
         :user "my-blacked-out-user-name1"
         :password "my-blacked-password1")
        (pop
         :server "pop.mail.yahoo.ca"
         :user "my-blacked-out-user-name2"
         :password "my-blacked-password2"))

I believe MAILHOST is set in mail-source.el in mail-source-fetch-pop.  I
don't know why it needs to be set if I am using pop3.el .

The reason that this is a problem for me is that future mail from my
local user appear as `From: monte@pop.eastlink.ca' .



In GNU Emacs 24.3.1 (i686-pc-linux-gnu, GTK+ Version 3.4.2)
 of 2013-04-15 on cletus
System Description:     Debian GNU/Linux 7.0 (wheezy)

Important settings:
  value of $LANG: en_CA.UTF-8
  locale-coding-system: utf-8-unix
  default enable-multibyte-characters: t

Major mode: Emacs-Lisp

Minor modes in effect:
  shell-dirtrack-mode: t
  erc-fill-mode: t
  erc-track-mode: t
  erc-autojoin-mode: t
  display-time-mode: t
  tooltip-mode: t
  mouse-wheel-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  column-number-mode: t
  line-number-mode: t
  transient-mark-mode: t

Recent input:
~ ESC [ 6 ~ ESC [ 6 ~ ESC [ 6 ~ ESC [ 6 ~ ESC [ 6 ~ 
ESC [ 6 ~ ESC [ 6 ~ ESC [ 6 ~ C-s s e t e ESC x r e 
p o r t TAB RET C-g ESC x g n u s RET ESC x g e t e 
n v TAB RET M A I L H O S T RET q y ESC x ESC O A RET 
ESC O A RET ESC x s e t e n TAB RET M A I L H TAB RET 
RET ESC x ESC O A ESC O A RET ESC O A RET C-h i m g 
n u s RET C-s o p DEL DEL p o p RET C-s C-s C-s C-s 
C-s C-s C-s C-s C-s C-s C-s C-s C-s C-s C-s C-s C-s 
C-s C-s C-s C-s C-s C-s C-s C-s C-s C-s C-s C-s C-s 
C-s C-s C-s C-s C-s C-s RET ESC [ 6 ~ ESC [ 6 ~ ESC 
[ 6 ~ ESC [ 5 ~ ESC [ 6 ~ ESC [ 6 ~ C-x b C-g C-x C-f 
. g n u s TAB C-a C-k ~ / . g n u s TAB RET ESC O B 
ESC O B ESC O B ESC O B ESC O B ESC O B ESC O B ESC 
O B ESC O B ESC O B ESC O B ESC O B ESC O B ESC O B 
ESC O B ESC O B ESC O B ESC O B C-x b RET C-x b m a 
i l TAB RET C-r s e r v e r ESC x r e p o TAB r t TAB 
RET

Recent messages:
pop.eastlink.ca
Are you sure you want to quit reading news? (y or n)  y
(No changes need to be saved)
pop.eastlink.ca

Composing main Info directory...done
Mark saved where search started [2 times]
Quit
Mark saved where search started
Making completion list...

Load-path shadows:
/usr/local/share/emacs/site-lisp/flim/md4 hides 
/usr/local/share/emacs/24.3/lisp/md4
/usr/local/share/emacs/site-lisp/flim/hex-util hides 
/usr/local/share/emacs/24.3/lisp/hex-util
/usr/local/share/emacs/site-lisp/flim/hmac-def hides 
/usr/local/share/emacs/24.3/lisp/net/hmac-def
/usr/local/share/emacs/site-lisp/flim/sasl-digest hides 
/usr/local/share/emacs/24.3/lisp/net/sasl-digest
/usr/local/share/emacs/site-lisp/flim/sasl-ntlm hides 
/usr/local/share/emacs/24.3/lisp/net/sasl-ntlm
/usr/local/share/emacs/site-lisp/flim/sasl-cram hides 
/usr/local/share/emacs/24.3/lisp/net/sasl-cram
/usr/local/share/emacs/site-lisp/flim/sasl hides 
/usr/local/share/emacs/24.3/lisp/net/sasl
/usr/local/share/emacs/site-lisp/flim/ntlm hides 
/usr/local/share/emacs/24.3/lisp/net/ntlm
/usr/local/share/emacs/site-lisp/flim/hmac-md5 hides 
/usr/local/share/emacs/24.3/lisp/net/hmac-md5

Features:
(shadow sort bbdb-message mail-extr jka-compr info emacsbug sendmail
misearch multi-isearch help-mode mm-archive url-http url-gw url-cache
url-auth url-handlers tramp-cache tramp-sh network-stream starttls tls
pop3 nnrss xml mm-url url url-proxy url-privacy url-expand url-methods
url-history url-cookie url-domsuf url-util url-parse url-vars nndraft
nnmh nnfolder bbdb-gnus nnnil gnus-agent gnus-srvr gnus-score score-mode
nnvirtual nntp gnus-cache org-publish org-exp ob-exp org-exp-blocks
org-agenda org warnings ob-tangle ob-ref ob-lob ob-table org-footnote
org-src ob-comint ob-keys org-pcomplete org-list org-faces org-entities
noutline outline org-version ob-emacs-lisp ob org-compat org-macs
ob-eval org-loaddefs find-func cal-menu calendar cal-loaddefs tramp
tramp-compat tramp-loaddefs shell pcomplete advice advice-preload
erc-fill erc-stamp erc-track erc-match erc-join erc-goodies erc
erc-backend erc-compat auth-source eieio cookie1 spam spam-stat gnus-uu
yenc gnus-msg gnus-art mm-uu mml2015 epg-config mm-view mml-smime smime
password-cache dig mailcap gnus-sum nnoo gnus-group gnus-undo nnmail
mail-source gnus-start gnus-spec gnus-int gnus-range gnus-win message
format-spec rfc822 mml mml-sec mm-decode mm-bodies mm-encode mail-parse
rfc2231 rfc2047 rfc2045 ietf-drums gmm-utils mailheader gnus-hardsort
gnus gnus-ems nnheader gnus-util time-date mail-utils mm-util mail-prsvr
wid-edit bbdb-mua bbdb-com mailabbrev bbdb timezone bbdb-loaddefs
w3m-load slime byte-opt bytecomp byte-compile cconv derived help-fns
edmacro kmacro easy-mmode easymenu pp comint ansi-color ring hyperspec
cl-macs gv thingatpt browse-url cl cl-lib time server tooltip ediff-hook
vc-hooks lisp-float-type mwheel x-win x-dnd tool-bar dnd fontset image
regexp-opt fringe tabulated-list newcomment lisp-mode register page
menu-bar rfn-eshadow timer select scroll-bar mouse jit-lock font-lock
syntax facemenu font-core frame cham georgian utf-8-lang misc-lang
vietnamese tibetan thai tai-viet lao korean japanese hebrew greek
romanian slovak czech european ethiopic indian cyrillic chinese
case-table epa-hook jka-cmpr-hook help simple abbrev minibuffer loaddefs
button faces cus-face macroexp files text-properties overlay sha1 md5
base64 format env code-pages mule custom widget hashtable-print-readable
backquote make-network-process dbusbind dynamic-setting
system-font-setting font-render-setting move-toolbar gtk x-toolkit x
multi-tty emacs)

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