Gmail can apparently be accessed by POP3 or IMAP. So you need a mail server that does SMTP, POP3, IMAP, and can use SSL. I would assume most of the common ones do; my only experience is with Courier MTA, which does (contra some older online material, courier does support SSL; that's the only way I use it).
The courier documentation is good; I have no notes on it indicating I've had no problems. It is primarily man pages, however, so first you will want to go through the "Install" link up top.
Also is it possible to send emails to gmail without a SSL certificate?
This brings us to a bit of a catch. You mention the need for "1 or 2 outgoing email address". If these are just gmail addresses, then you don't need a mail server at all, you just need a mail client. I am sure you can configure any normal mail client to retrieve from, and send through, gmail if that's what you really want.
If you meant you want to set up email addresses of your own, you'll probably need a real domain name to put after the
@. Technically, you can use things like
me@[123.456.789], but I am not sure how accepting of this other mail server are. In any case, if you want to use SSL, you absolutely will need a certificate for the server which requires a registered domain name. Note that this is a separate issue than a client connecting to gmail, which does not require this.
As per Faheem's comment, if you want the server so you can send mail directly but have the replies go through gmail (meaning, no custom domains), you should not need a certificate to use SSL since the server is acting as a client of the server the mail is being delivered to.