email problems after going back to old version

hi i need a little help here
when i first installed zencart all emails worked in the admin area and customers got the welcome emails but all this stopped working when i tried to upgrade to v1.5 which failed to work so i re-installed v1.3.9 that i had backed up and from that point on the whole email sending stopped working
this has got nothing to do with the host as i have another zencart v1.5 installed on the same sever with different database and that works great so it has to be something within the cart
i have compared all the settings between the 2 versions and they all match

any ideas are welcome as this is now becoming a nightmare

thanks in advance

Definitely bizarre.

I never recommend going backwards to older versions. Lots of problems can occur when doing that.

As for fixing your current problem, this is where I'd start: http://www.zen-cart.com/wiki/index.php/Troubleshoot_-_Diagnosing_Obscure_Issues