Does anyone know of an online (free!) tool which lets you check your email mailers similar to IETester or browsershots but to test for how they will look in outlook express, hotmail, gmail etc?

 

I don't think there is, but would be good to know!

http://www.emailonacid.com

 

Allow you to test a couple email clients for free, however its only a couple and if you want comprehensive testing you definitely need a paid solution like email on acid's paid system or Litmus.

 

Another useful free tool however is http://inlinestyler.torchboxapps.com/ Not only will it move your css inline automatically (needed for gmail etc), but it also warns you about incompatibility with any CSS rules you have used.