exchange 2013 not forwarding outbound emails

Good Day,

We are having an issue with emails not being forwarded outbound by Exchange 2013.

Scenario: We have users that need emails delivered to external email addresses (i.e.
These users are in our Exchange Server as contacts so when an email comes in to the email should be redirected to their external gmail account.

Problem is for some users we are receiving NDRs. We were not experiencing this issue before we migrated from Exchange 2010 earlier this year.


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Adam FarageEnterprise ArchCommented: is forwarding (within the mailbox) to correct? what is the NDR you are receiving?
Zacharia KurianAdministrator- Data Center & NetworkCommented:
If the issue exists "internally"  only , may be you have to clear the Outlook Autocomplete Cache, from these users who get NDRS. Let them try sending by selecting the address from the GAL.
BrockstedtAuthor Commented:
The users in question do not have a mailbox on our Exchange - only reside as contacts, however, they require a company email address which needs to be forwarded to their external email.

The way it had been working prior to the migration was an email to would hit our Exchange, Exchange would recognize this user as a contact and forward the email to the external address on their contact card.
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Zacharia KurianAdministrator- Data Center & NetworkCommented:
could you post the NDR message? That would throw some lights to the issue.
Zacharia KurianAdministrator- Data Center & NetworkCommented:
the possible reasons could be, wrong external email address or message size restrictions. To pinpoint the issue please post the NDR message.
BrockstedtAuthor Commented:
Good Day Zacharia,

I will retrieve one of the NDRs and get it posted.

BrockstedtAuthor Commented:
Good Day,

I am attaching a NDR for review. User in question will be Adrian Gilmore. Please see scenario below:

Email entered our system from John bordeaux <>
to Adrian Gilmore <>
which forwards to a Contact in our Exchange, Contact has external address of

NDR states following error: Your message couldn't be delivered because you weren't recognized as a valid sender. Make sure your sending address is set up correctly and try to send the message again. If the problem continues, please contact your helpdesk.
If you check on your ECP on 2013 you can't forward emails to contacts from there.

You should re-establish the forwards using PowerShell:

Send email to mailbox and forward to SMTP account:

Set-Mailbox -Identity "USERNAME" -DeliverToMailboxAndForward $true -ForwardingSMTPAddress

Receive email and forward to SMTP account only:

Set-Mailbox -Identity “USERNAME” -DeliverToMailboxandforward $False -ForwardingSMTPAddress

Receive email and forward to email account only:

Set-Mailbox -Identity “USERNAME” -DeliverToMailboxandforward $False -ForwardingSMTPAddress  $Null -ForwardingAddress

This command will STOP the forward of all emails from the mailbox “USERNAME”:

Set-Mailbox -Identity “USERNAME” -DeliverToMailboxandforward $False -ForwardingSMTPAddress  $Null -ForwardingAddress $Null
Zacharia KurianAdministrator- Data Center & NetworkCommented:
I am attaching a NDR for review. User in question will be Adrian Gilmore

Make sure the user "Adrian Gilmore" is either a mail box user or a mail enabled user in your exchange. Because external forwarding can be done either to a mail box user or mail enabled user.

The 1st error you got  
Your message couldn't be delivered because you weren't recognized as a valid sender. Make sure your sending address is set up correctly and try to send the message again. If the problem continues, please contact your helpdesk.
clearly tells you this.

So try creating the specific user either as a mailbox user or mail enabled user.

For a more clarity purpose, see how the other users created in your exchange and compare them with the problematic user.
BrockstedtAuthor Commented:
I will create another mail user, however, I noticed Adrian Gilmore is a mail user. Does this mean we need to make them all mailboxes?
At this point I will suggest you to go with the less complicated for you and your deployment.

Yes, you can go ahead and create mailboxes for the accounts you need this to work just make sure to hide it from the address book and set the forward to send to the contact and not the mailbox as the mailbox can become an issue as it is not maintained by a person on the organization.

Also, if there are not too many cases you can use the contacts you already have and create a rule per case that for every recipient needed it will redirect the message to the contact.

Step by step for the rule:

Open you ECP
Go to Mail Flow
Select rules
Select and Click the "+" to create a new rule
Give a name to the rule
From the Apply this rule if...  select The recipient is...
From the popup window go to the end of the window and write the email of the person (like and click ok
Now from the new rule window...  select Do the following...  and select Redirect the message to...
From the popup window look for and select the contact for this particular rule (like click
Click Save

Either option requires time for setup but the last one less maintenance.

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