Milter-greylist

> > selector1._domainkey.outbound.protection.outlook.com
> ;; Truncated, retrying in TCP mode.
> Server:         127.0.0.53
> Address:        127.0.0.53#53
> 
> Non-authoritative answer:
> *** Can't find selector1._domainkey.outbound.protection.outlook.com: No answer

You must have an issue with the domain name resolution. Try to fix it. For me it just works:

$ dig +short txt selector1._domainkey.outbound.protection.outlook.com.
;; Truncated, retrying in TCP mode.
"v=DKIM1\;k=rsa\;p=MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAvWyktrIL8DO/+UGvMbv7cPd/Xogpbs7pgVw8y9ldO6AAMmg8+ijENl/c7Fb1MfKM7uG3LMwAr0dVVKyM+mbkoX2k5L7lsROQr0Z9gGSpu7xrnZOa58+/pIhd2Xk/DFPpa5+TKbWodbsSZPRN8z0RY5x59jdzSclXlEyN9mEZdmOiKTsOP6A7vQxfSya9jg5" "N81dfNNvP7HnWejMMsKyIMrXptxOhIBuEYH67JDe98QgX14oHvGM2Uz53if/SW8MF09rYh9sp4ZsaWLIg6T343JzlbtrsGRGCDJ9JPpxRWZimtz+Up/BlKzT6sCCrBihb/Bi3pZiEBB4Ui/vruL5RCQIDAQAB\;n=2048,1452627113,1468351913"
$