Our Exchange 2016 Full Hybrid without MB migration delivers some mail to quarantine

Copper Contributor

We have a Full Hybrid Configuration including:

Exchange classic Hybrid Topology,

Configure my CAS and Mailbox servers for transport

Receive Connector Configuration (all servers)

Send Connector Configuration (all servers)

We have NO mailbox migrations to the cloud, not yet.

The only functionality required is for Teams Calendar usage.


Some of our recipients, always 365 Tenants notice a SPF failure the likes and the messages are either not delivered (dropped) or end up in Quarantine.

Since our government agency don't believe in implementing SPF yet since we are not using EOL or migrated mailboxes, this is not an option.


Is there a way to get solve this issue with those M/O365 Tenants?

Is Enhanced Connector Filtering an option here?

How does the data flow, I thought that since we're not using EOL, the transport from On-Prem --> Directly to external mailboxes/mail servers, it seems to be going from On-Prem --> EOL --> external mailboxes/mail servers. Is this correct?


It's a small group but they are irritated and we rolled back the HCW for now.


Thanks in advance.

1 Reply
best response confirmed by TimothyCor (Copper Contributor)

Seems to be working.

I don't know how or why.

Case closed.