Lots of sent email going to spam

[#1]

I have my own domain for email usage but send via relay.plus.net.

my SPF, DKIM and DMARC are all good a set up in my domain control panel ( netnerd ) as can be seen in this header from an email sent to gmail

It seems to be emails sent to aim.com and microsoft domains that suffer from it the most.

[#2]

One of the emails, which was a reply to an email about going for a few drinks and was sent to 7 people simply contained the words

Not Me

[#3]

I have my own domain for email usage but send via relay.plus.net.

my SPF, DKIM and DMARC are all good a set up in my domain control panel

SPF may be ok, but DKIM wont work via relay.plus.net from an external domain