openvpms.org has no spf record in its DNS entry. This can cause emails to be discarded. See
https://support.sendgrid.com/hc/en-us/articles/202517236-SPF-Records-Explained

Note the our DNS entry appears to have other minor problems as well:
a) the mx record refers to newserver.openvpms.org, not openvpms.org
b) checking services like http://mxtoolbox.com/SuperTool.aspx?action=smtp%3aopenvpms.org&run=toolpage# show various other minor errors