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Fixes for shared-mailbox mail errors
Each page starts with the exact error text so you can confirm you're in the right place, explains what's actually happening, and gives the fix click by click.
550 5.7.520 Access denied — external forwarding
Microsoft 365 blocks auto-forwarding outside your organisation by default.
Google Groups: replies loop back to the group
Every reply lands back in the Collaborative Inbox and the customer gets nothing.
550 5.7.133 RequireSenderAuthenticationEnabled
Your distribution group rejects mail from outside the organisation.
Recipients get a winmail.dat attachment
Outlook sent the message in TNEF format and nothing else can read it.
How to share a support inbox without sharing a password
The four ways to give a team one address, and what each one costs you.
These come up most often on an address several people share.
Bosun is a shared inbox built for exactly that,
if you want one.