How to enable inbound external email forwarding to Mailbox in Office 365?

Question

Hello All,

Relatively new to this process and SysAd World, so please bear with me.

Situation is the following: Within my corporation I needed to create a dedicated Mailbox within our Tenant to allow the receipt of external emails with attachments so my relevant team can process with OCR imaging. Mailbox was created, but external users were reporting the 550 5.7.520 error when receiving undeliverable messaging. This mailbox needs to be able to receive these attachment emails from our external customers to fulfill their needs, but Defender's default Anti-Spam policies as we have them currently set up is most likely preventing all of this from coming through.

Is there someway we can leave our default policies in place and simply exclude this individual mailbox from said policy so it can successfully receive external/forwarded emails with attachments? I understand the potential security risks for doing so, and am exploring every possible option, but I wanted to confirm with more knowledgeable experts on the feasibility of this ask.

Answer 1

Hi, the easiest thing if you want to exclude one mailbox from anti-spam is to add that mailbox as an exception in your policy: https://learn.microsoft.com/en-us/microsoft-365/security/office-365-security/anti-spam-policies-configure?view=o365-worldwide