exchange mail contacts and shared smtp

Question

I need to have multi mail contacts all forwarding out to a separate domain (smtp address).

error:
The proxy address "SMTP:test1@do.com" is already being used by the proxy addresses or LegacyExchangeDN of "do.com/users - Contacts/test1". Please choose another proxy address.( The "MailContact" with display name "test1" is already setup and using the same address.)

thanks

Answer 1

I created a mail contact record with inhouse primary smtp address and then modified the AD attribute MailRoutingAddress to route mail externally

Answer 2

Hi @Efff dd

According to the error information above, we will need to find which mailbox/recipient is using the proxy address, then remove the proxy address from other mailbox/recipient.

Get-Recipient | where {$_.EmailAddresses -match "test1@do.com"}

Or

Get-Mailbox test1@do.com | fl UserPrincipalName,EmailAddresses

Below are the links which discussed about this similar issue:
How to fix conflicting proxy addresses in O365 when creating a mailbox
The proxy address is already being used by the proxy address of another mailbox

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