/errors/exchange-online/proxy-address-already-being-used
The proxy address "SMTP:user@contoso.com" is already being used by the proxy addresses or LegacyExchangeDN
- tool
- Exchange Online PowerShell
- versions
- Exchange Online, ExchangeOnlineManagement 3.x
- os
- windows, linux, macos
The proxy address "SMTP:user@contoso.com" is already being used by the proxy addresses or LegacyExchangeDN. Please choose another proxy address. means another recipient in your organization already has that email address. In Exchange an address (a "proxy address") can belong to only one recipient. Find the object that holds it:
Get-EXORecipient -Filter "EmailAddresses -eq 'smtp:user@contoso.com'" |
Format-List DisplayName,RecipientTypeDetails,PrimarySmtpAddressRemove the address from the other object
Use the Set- cmdlet that matches the RecipientTypeDetails value you found. For a mailbox:
Set-Mailbox -Identity "Shared Sales" -EmailAddresses @{Remove='smtp:user@contoso.com'}Then add the address where you wanted it:
Set-Mailbox -Identity "John Woods" -EmailAddresses @{Add='smtp:user@contoso.com'}SMTP: in capitals marks the primary address and smtp: in lower case a secondary one. You cannot remove the primary address of an object; change its primary address first.
| RecipientTypeDetails | Cmdlet to change addresses |
|---|---|
| UserMailbox, SharedMailbox, RoomMailbox | Set-Mailbox |
| GroupMailbox (Microsoft 365 group) | Set-UnifiedGroup |
| MailUniversalDistributionGroup, MailUniversalSecurityGroup | Set-DistributionGroup |
| MailUser, GuestMailUser | Set-MailUser |
| MailContact | Set-MailContact |
Nothing is found
If the filter returns nothing, the address is usually on a deleted object:
Get-EXORecipient -IncludeSoftDeletedRecipients -Filter "EmailAddresses -eq 'smtp:user@contoso.com'" |
Format-List DisplayName,RecipientTypeDetails,PrimarySmtpAddressA soft-deleted mailbox or Microsoft 365 group keeps its addresses until it is restored or purged. In hybrid organizations, objects synced from on-premises Active Directory must be changed on-premises (the proxyAddresses attribute); changes made in the cloud are overwritten by the next sync.