I'm going to break your question into two parts:
- Where can I send test email?
Send test email to a disposable email address service.  These services automatically create an inbox for any email you send to them. You can then read the messages in the inbox through their web site, without registration and without a password.
For example, I can send an email to to
foo@<some-provider>, then go to
http://www.<some-provider>/foo/inbox to read the message.
Note that the messages are only stored for a short time, so it's best to check shortly after you've sent them. Also note that the inboxes are completely public and anyone can read the messages you send, so don't send anything you want to keep private.
- How can I avoid having my messages marked as spam?
This is much trickier, because no email service wants to reveal exactly how they combat spam. Here are just a few things that you should do:
- Use double-opt in: When someone signs up for your email, send them an email message with a verification link. Don't send them any additional emails unless they verify their account first.
- Don't wait too long to send messages so that users don't forget that they signed up for your service and then complain that they're getting spam.
- Include an opt-out link in every message you send.
- Stick to the schedule your recipients agreed to. If your recipients signed up for monthly messages, don't start sending messages every week.
- Set up a Sender Policy Framework (SPF) Record.
This isn't everything, but should give you a good start.
: Google for "disposable email service".