iCloud bouncing emails sent from our server

We have succesfully configured and tested for DKIM and SPF.

relay=mx6.mail.icloud.com[17.172.34.71]:25, delay=2.3, delays=0.09/0.02/0.96/1.2, dsn=5.7.1, status=bounced (host mx6.mail.icloud.com[17.172.34.71] said: 550 5.7.1 Message rejected due to local policy. Please visit https:/

We are using the latest version of PHPMailer to send emails over SMTP.

Unlocktheinbox.com's test shows passed at basically everything except:

- SSLv3 Disabled: No - You should Disable SSLv3 - It's open to the POODLE Vulnerability.

And a few warnings, like this:

Content-Transfer-Encoding: NOT FOUND 7bit encoding will be assumed - Since Missing

I have no idea what could be the reason, any suggestions?