My emails are being categorized as spam by gmail and gmail returns them

[GoogleBot42]

The title says it all. Everything has been setup in my mailinabox. Lets Encrypt has been setup. The dns resolves to its IP. (I receive mail just fine)

Here is the email it sent back to me

This is the mail system at host box.*****.***.

I'm sorry to have to inform you that your message could not
be delivered to one or more recipients. It's attached below.

For further assistance, please send mail to postmaster.

If you do so, please include this problem report. You can
delete your own text from the attached returned message.

                   The mail system

<s*********@gmail.com>: host gmail-smtp-in.l.google.com[74.125.28.27] said:
    550-5.7.1 [138.***.***.***      12] Our system has detected that this
    message is 550-5.7.1 likely unsolicited mail. To reduce the amount of spam
    sent to Gmail, 550-5.7.1 this message has been blocked. Please visit
    550-5.7.1  https://support.google.com/mail/?p=UnsolicitedMessageError 550
    5.7.1  for more information. r63si8120314plb.39 - gsmtp (in reply to end of
    DATA command)

[ANC]

Did you add the SPF data in a TXT record as recommended by MIAB?

[GoogleBot42]

No, how do I do that?

[ANC]

Look at External DNS when logged into your box.xxxx.xxx server.

Wherever you do the DNS for the domain you should add a TXT records with this:

v=spf1 mx -all

This may help:

https://productforums.google.com/forum/#!msg/gmail/17EYTKyl7LM/CMBpLr9n0pEJ

and if not maybe something here:

http://bit.ly/2iS6GOR