Welcome email for new account sign up

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the welcome email doesnt send when customer create new account..where do i enable it???

 

aslo where do i place cache diretory

 

when i go to cache control i got this error

 

Error: Cache directory does not exist. Please set this Configuration->Cache

 

i try create a cache dirctory tmp

 

/catalog/tmp

/catalog/admin/tmp

/catalog/admin/includes/tmp

 

but non of them work not sure where that need to be place