Considering it is a new domain, the first thing to look at would be the IP address of the server that the domain resolves to. If you are on a shared server (siteground, Justhost, godaddy etc..) it's possible that another account on the same server has been flagged as a spam source, and that could be why your being flagged as spam when sending a message from the same ip.
I have a tremendous amount of experience sending emails from new domains - perhaps 2,000,000 emails per year - and the long and short of it is this: email deliverability is tremendously complex.
Why? For one thing, because of the constant battle between spammers, ISPs, ESPs and other players, among other things. Also, because email still uses some very old and outdated protocols that make this all more difficult.
If your business is going to rely heavily on email, I would encourage to educate yourself now so that you won't be stymied as you grow. Many of the things I learned were through trial and error - which can be excruciatingly frustrating.
Just a few of the things you should immediately begin working on: proper SPF, SenderID, DKIM compliance along with solid DNS set up. Additionally, if you will use email heavily, I would start now putting the pieces in place for later white labeling aa nd possible dedicated IP sending. In terms of the actual email content itself, that is another subject you will want to investigate.
I'm not saying these things to discourage you - but rather to help you avoid the mistakes we made in the past.
If you need a hand getting a little grip on this I probably can steer you in the right direction pretty quickly.
Wish you the best in your endeavor!
There are a lot of factors at play when getting caught in the junk folder. Long term, send quality content to trusted emails. In the short term, make sure the URLs you are sending people to match the domain you are sending from? Also, what subject line were you using? Also, what vendor are you sending from?