My cpanel at my webhost sometimes sends me email if, for instance, a certificate isn’t going to be renewed. Currently it has mail.mydomain.com pointing to its local smtp server, which gets rejected because it isn’t authorized. The domain editor requires an IP V4 address. It won’t accept mail.runbox.com - I can’t find the appropriate address in the FAQ or documentation.
What is a proper ipv4 smtp server address?
Could you open a ticket at https://support.runbox.com for this please and I’ll deal with it personally as I need to ask a few questions about this to fully understand your set up.
If you are talking about using an SPF record for your domain so that the Runbox servers are accepted as sending for your domain then you can find details here Runbox Sender Policy Framework settings | Runbox Help you wouldn’t use a single IP address as we have more than one for our outgoing servers.
I have a feeling I’ve misunderstood what you are doing though so a ticket would be better. Thank you.