If you get error like:
WARNING: channel "pear.php.net" has updated its protocols, use "channel-update pear.php.net" to update pear/Mail requires PEAR Installer (version >= 1.5.6), installed version is 1.5.0 No valid packages found install failed
update PEAR as:
pear channel-update "pear.php.net"
That should fix the warning.
Probably then, if you will feel comfortable, you can also upgrade to a latest version of PEAR with,
pear upgrade-all
The upgrade is just to make sure all components you have latest changes in PEAR with them.
if you still get error:
pear/Mail requires PEAR Installer (version >= 1.5.6), installed version is 1.4.9
No valid packages found
install failed
Do:
First: pear upgrade --force pear
Then: pear install --alldeps Mail