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Use SMTP Relay to route outbound SES emails through to Exchange Online

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Hi Everyone,

We currently use SES to send emails to recipients using our registered Route53 domain (say "noreply@ourcompany.co.uk"). We currently send emails to a client (such as "client@theclient.co.uk").

The client would like us to leverage a capability of sending emails through to their email distributions lists to multiple internal recipients, though the challenge we have here is that the distribution lists are not permitted to receive email from 'external' email senders.

The client's email capability is set up on Exchange Online, and I was seeking some advice whether it was at all possible to use an outbound SMTP relay to effectively route our emails from SES to the client's Exchange Online instance so that emails to the @theclient.co.uk would effectively be managed/received from an "internal" address.

Having looked through the documents for the SES SMTP relays, there seems to be multiple reference to managing inbound SMTP relays through Mail Manager, but I can't seem to find any clarity on routing outbound emails sent from SES through an SMTP Relay to another mail service such as Exchange.

I do hope that makes sense, and if anyone has any insights in whether this is indeed possible it would be much appreciated.

Many Thanks,

asked 3 months ago126 views
1 Answer
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In order to send mail as an "internal" user in Microsoft 365 Exchange Online, the sender must authenticate via OAuth2 to a valid mailbox in the Exchange Online tenant. The mailbox user must have the necessary permissions to send to each recipient at the desired volume.

The SES Mail Manager SMTP Relay action does not support authenticating via OAuth2 at this time.

However, it is possible for the tenant administrators to configure Exchange Online to allow-list SMTP relayed traffic from SES Mail Manager, and that is summarized by this blog https://aws.amazon.com/blogs/messaging-and-targeting/how-to-use-ses-mail-manager-smtp-relay-action-to-deliver-inbound-email-to-google-workspace-and-microsoft-365/

AWS
answered 3 months ago

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