DomainKeys Identified Mail (DKIM) and Sender Policy Framework (SPF) are two technologies which play especial role for your Newsletters, effects highly on your open rate, Spam Score and may cause successful Newsletter hit right to the subscriber’s inbox.
These technologies serve to check whether Send From: firstname.lastname@example.org address that is used in the email you have sent was authorised by your site domain.
You can solve this issue by setting up authentication of DKIM and SPF via host’s control panel (Plesk, cPanel, WHM etc.) at your server’s DNS records by adding TXT entries.
Your subscriber email services use SPF to verify the address you sent your email from and it’s authentication by your site domain. In the case you are going to send your newsletter via third party service you’d better add their DKIM and SPF to DNS records of your server.
Absence of this TXT entries may prevent sending Newsletters with From Address email@example.com from your site super-site-by-me.com .
So, what is going on after you sent Newsletter with contacts like above? When email server receive this letter it controls whether you are authorized to use firstname.lastname@example.org from site super-site-by-me.com. Since there is no email server you send to have no SPF records on your site, the answer is your newsletter is no authorized and in mostly it will get straightly to subscribers spam folder.