CODEWITHSUNDEEP
emailoutlookoffice365exchange-server
insane_IT
insane_IT

Reputation: 73

Office 365 Hybrid Mailflow

i want to use Office 365 / Exchange Online in hybrid with on-prem Mailrelay. The Mailflow is very confusing, what is best practice?

Incoming:
WWWW -> Thirt-Party MTA -> Exchange Hybrid (on-prem) -> Exchange Online (cloud) -> Cloud Mailboxes
WWWW -> Thirt-Party MTA -> Exchange Hybrid (on-prem) -> Outlook

I am not sure if A or B is the best practice.

Outgoing:
Outlook -> Exchange Hybrid (on-prem) -> Thirt-Party MTA -> Exchange Online (cloud) -> Cloud Mailboxes
A) Outlook -> Exchange Hybrid (on-prem) -> Thirt-Party MTA -> Exchange Online (cloud) -> External Mailboxes
B) Outlook -> Exchange Hybrid (on-prem) -> Thirt-Party MTA -> External Mailboxes

I also read that its not possible to have a Thirt-Party MTA beetween Exchange Hybrid and Exchange Online is that true?

Upvotes: 0

Views: 648

Answers (1)

Hannes Palmquist
Hannes Palmquist

Reputation: 26

Third-party MTA: Only Exchange Edge is supported as SMTP gateway for Exchange onprem <-> Exchange online hybrid traffic.

Flow direction: For simplicity you should either use centralized mail transport or non-centralized mail transport.

Centralized mail transport (Inbound and Outbound via Exchange onprem)

Inbound: Internet -> SMTP gateway (third-party MTA is ok) -> Exchange Hybrid -> Onprem mailboxes Inbound: Internet -> SMTP gateway (third-party MTA is ok) -> Exchange Hybrid -> Hybrid SMTP connector (direct or via Edge) -> Online mailboxes

Outbound: Onprem mailboxes -> Exchange Hybrid -> SMTP gateway (third-party MTA is OK) -> Internet Outbound: Online mailboxes -> DHybrid SMTP connector (Direct or via Edge) -> Exchange Hybrid -> SMTP gateway (third-party MTA is ok) -> Internet.

The key is that the SMTP traffic between Exchange Online and the Exchange onprem server should either be direct or via exchange edge.

Non-centralized mail transport (inbound and outbound to internet via Office 365)

Inbound: Internet -> Exchange Online -> Online mailboxes Inbound: Internet -> Exchange Online -> Hybrid SMTP connector -> Exchange Hybrid -> Onprem mailboxes

Outbound: Online mailboxes -> Exchange Online -> Internet Outbound: Onprem mailboxes -> Exchange Hybrid -> Hybrid SMTP connector (either direct or via Exchange Edge) -> Exchange Online -> Internet

Upvotes: 1

Related Questions