Sorry for the problems with your Apple Mail client. I actually am a long time MacBook Pro user myself, though I've typically avoided the Apple Mail client for managing mail. I went and re-tested this issue on my own VPS and in the process I created a video about it. The video is titled "Setting Up the Apple Mail Client with a VPS", but I verify that the outgoing mail works in the process. I use the VPS settings and show you how to stop those certificate warnings as well. If you require more info on a summary of the email settings, please see How to find your email settings. Also, please make sure to review the article dealing with problems sending email.
The video was just finished, so it's possible that YouTube is still processing it, but hopefully, it should help resolve your problem. The main difference is that I'm using the latest version of Yosemite on my MacbookPro with the Apple Mail client version 8.2. I have no access to the earlier version. The setup is basically the same, though. If you continue to have problems then we can double-check here by setting up an email directly with your VPS. Beyond that, it would be suggested that you talk with Apple support.
If you do continue to have problems after reviewing the video, then please let us know so that we can investigate the issue in more depth.
Like this Question? Tweet
Related ArticlesIMAP Issues Affecting Outlook 2013 and Office 365
SMTP and ESMTP Error Code List
Request a De-listing from a Blacklist
Why do mail servers get blacklisted?
Send mail via Gmail when server IP is blocked