Bash script to loop through all the different platforms/sites on an aegir deployment, and performs drush commands against them.

Running a drush command on all sites in multisite aegir installation

#!/bin/bash

for dir in /var/aegir/platforms/*
do
  cd "$dir/sites"
  drush @sites -y ev "variable_set('smtp_host', 'your_host');"
  drush @sites -y ev "variable_set('smtp_username', 'your_user');"
  drush @sites -y ev "variable_set('smtp_password', 'your_pass');"
  drush @sites -y ev "variable_set('smtp_port', 'your_port');"
done