Where to get older versions of pkgs

[Harry Putnam <reader@newsguy.com>]

I'm having plenty of trouble with the newest version of sendmail on a
brand new install.

I have the version numbers obtained by running:

aptitude search -F sendmail '%p %v'

On a machine with it installed.  I understand the command necessary to
install a certain version: aptitude install <pkg>=<version>
But when I run that, I'm told the pkgs cannot be found and it wants to
install the newer version 8.14.4-5 

All the sendmail group showning the version I want below:

  sendmail               8.14.4-4.1 
  sendmail-base          8.14.4-4.1
  sendmail-bin           8.14.4-4.1
  sendmail-cf            8.14.4-4.1    

I have it running on my main desktop with out problems and want to
install it on this new install.

Is it a question of expanding my sources.list? Or maybe the exact syntax
in detail is all that is lacking.

I tried several renditions  but I think it is:

  aptitude install sendmail=8.14.4-4

But maybe that is not present in the repo.  My current sources list is
the one a vanilla install has left me.  Well not quite vanilla since I
installed from an lxde iso: debian-testing-i386-lxde-CD-1.iso


  deb http://ftp.us.debian.org/debian/ jessie main
  deb-src http://ftp.us.debian.org/debian/ jessie main
  
  deb http://security.debian.org/ jessie/updates main
  deb-src http://security.debian.org/ jessie/updates main
  
  # jessie-updates, previously known as 'volatile'
  deb http://ftp.us.debian.org/debian/ jessie-updates main
  deb-src http://ftp.us.debian.org/debian/ jessie-updates main
  
  # jessie-backports, previously on backports.debian.org
  deb http://ftp.us.debian.org/debian/ jessie-backports main
  deb-src http://ftp.us.debian.org/debian/ jessie-backports main

Using this syntax... I get this result:

 # aptitude install sendmail=8.14.4-4
 
  Unable to find a version "8.14.4-4" for the package "sendmail"
  Unable to find a version "8.14.4-4" for the package "sendmail"
  The following NEW packages will be installed:
    sendmail sendmail-base{a} sendmail-bin{a} sendmail-cf{a} sensible-mda{a} 
  0 packages upgraded, 5 newly installed, 0 to remove and 0 not upgraded.
  Need to get 0 B/1,708 kB of archives. After unpacking 3,493 kB will be used.
  Do you want to continue? [Y/n/?]