I'm having I think the same issue. I have server logs on the recieving side I can share as well. here are the details
Here is my setup:
me@SenderServer.com to send the test mail
me@DestinationServer.com is the final destination address we are forwarding to and where server logs are recovered from
me@MyCloudron.io is set to forward to me@DestinationServer.comMyCloudron.io which has ip 18.104.22.168 is the cloudron install
NOTE: 22.214.171.124 is fake. The real IP is a dynamically changing IP address from the ISP which is likely spam blocked. Prior to setting up the STMP relay server no outgoing emails would work as they would be blocked on the destination server due to ISP's all adding dynamic ip blocks to spam lists by default. After setting up the relay I was able to send as me@MyCloudron.io, and that still works, just forwarding does not work. I suspect, or wonder, if sogo and rainloop are properly using the cloudron configured smtp relay?
MyCloudron.io is setup to forward mail through a posteo.de server using a paid account. This works fine for sending and recieving using me@MyCloudron.io directly but me@MyCloudron.io forward to me@DestinationServer.com fails.
"message": "554 kundenserver.de (mxeue112) Nemesis ESMTP Service not available No SMTP service IP address is black listed. For explanation visit https://www.ionos.com/help/index.php?id=2425&ip=126.96.36.199&c=bl"
@marcusquinn I think DNS automation (provider specific) atleast needs to come from elasticemail itself ideally. It's not possible to keep track of all the DNS records each provider wants to set and if it's even available with API. It's basically impossible to test on our side atleast.
@girish yeah, and I must have been through testing over a dozen of these services in one way or another now. I think a lot of the things people think are their own service are actually Elastic Email resellers.
@edapm Personally, I'm all-in with Hetzner, not free but the best value for features I've found, particularly having network DDoS protection as standard. Others recommended include Contabo and Scaleway.
If you're getting free (inclusive) stuff from Microsoft then I suppose that's decent. Personally, I'm all GitLab, so anything GitHub is second-choice.
I guess there's nothing truly free, including your time, but those are the options I recommend, otherwise it's support tickets to Azure and hope for their ability to allow for port needs.
And no, my mail relay does not accept IP whitelisting. It's not a proper mail relay service to be exact, but just a regular mail service with outgoing smtp for authenticated users.
Ah yes, someone was trying to do this with a gmail account as well sometime back (and more recently with a mailbox.org account). I think we have to implement this feature in Cloudron to make this use case work.