Sending mail to users from my site

I'm using AuthSMTP which is a paid SMTP Relay service. They only support a finite amount of "from" email addresses, which must be proper accounts.

This is my first site build and I'm trying to get my head around how to implement email.

When a user registers with the site or forgets their p开发者_如何学JAVAassword, I have an 'info' email account which these messages come from. This works.

However, how do I go about the contact form? I want the email to come from the user who filled in the contact box TO the info inbox. I need to be able to reply directly to them.

How can I do this is my server won't allow the email to come "from" the user? if I use the "reply-to" in the headers, what do I put for the "from" field?

put the email address you are logging in with