Hello, i have a weird situation.
i have two mbx servers and two cas servers, all 2013 belonging to one organization.
i have deployed an edge server and subscribed it successfully.
all receive and send connectors are normal, no authentication mechanism missing nor configuration.
mail flow internally is flowing fantastic, mail flow from internet to inside is going great, however, when i send an email from inside to the internet, the edge server rejects it a while later with a message delayed NDR, and the error on the report and the queue viewer is the following:
451 5.7.3 Cannot achieve Exchange Server authentication. Attempted failover to alternate host, but that did not succeed. Either there are no alternate hosts, or delivery failed to all alternate hosts
i have no clue why it's been like that, i am telnet-ing just fine between sites and all FQDN are correct, i have no clue what's the problem with authentication.
i have google countless hours, all solutions are pretty basic trivial and do not apply to my case as what they suggest is pretty trivial and no real sys admin can omit the suggestions they offer.
- Merged by Winnie LiangMicrosoft contingent staff, Moderator 21 hours 40 minutes ago duplicate