PhpList is an excellent application. As you need to setup unsubscribe, subscription links, handle bounces, keep records all to comply with anti-spam requirements. It is a bit complicated to setup (many settings and features). But other apps just pale or are costly. This is free.
I would recommend you to check your subscription size.
If you have a large subscription you can use aweber.
If you have a relatively smaller subscription I would recommend mailchimp.
Also if the subscription size is very small you can just import the contacts in Email and send it via Mail merge using Outlook. You can do this easily by making sets of 20-50 contacts.