Avoiding 'on behalf of' sender in Office 365

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How to stop Office 365 sending emails with ‘on behalf of’ in the sender or FROM line.

One major hassle with Office 365 is that messages sent using connected accounts don’t have a normal ‘FROM’ line. Instead they show the Office 365 internal domain ‘ on behalf of’ your connected account.

For example an Office 365 user in the @contoso.onmicrosoft.com domain has a connected account [email protected] sends an email out ‘from’ the latter address – here’s how it will look to a receiver:

Fred Dagg  on behalf of Fred Dagg 


For many email programs this long line will scroll off the edge of the window. In any event, it’s likely to be confusing or suspicious to the receiver. When they Reply the return message will go to the ‘on behalf of’ address (eg [email protected] )

(Gmail does the same thing when you link an address to a Gmail account. You can send messages from a linked address but the same ‘on behalf of’ line will appear in the message header)

The ‘on behalf of’ FROM address is the major weakness in Office 365’s connected accounts feature. Connected Accounts is a great way to import messages from existing accounts but the downside is a problem.

There’s only two official ways to avoid ‘on behalf of’. One is to switch to using the Office 365 internal domain for all email – which isn’t really a good solution at all.

The other solution is to switch your entire domain (eg @freddagg.com) over to Office 365. Only when Office 365 controls the domain name will it let you send out ‘clean’ FROM showing only the one address.

Problem is, adding a domain to Office 365 is a major move. It affects all email for the domain. There’s no easy way to move some domain email users to Office 365 leaving others with the existing mail setup. There are ‘hybrid‘ options available but these only apply if you have Exchange Server running ‘in-house’ and want to move some users to Office 365.

Office 365 provides good step-by-step instructions for adding a domain and configuring email. However you need to be clear about what email hosting and aliases you have on the existing domain before migrating.

Unofficial fix

An alternative and unofficial fix is to use Outlook.  You could create a second POP/IMAP plus SMTP account in Outlook to operate alongside the Office 365 connection. That connection would probably use the pre-migration details for the email address (eg via an ISP?).  The incoming email connection has to work but should be configured to receive no email (ie an empty mailbox).

Outgoing messages can go out via the SMTP connection, using the full email address, rather than via Office 365 with ‘on behalf of’.

This fix will let you send ‘clean’ FROM emails via Outlook but won’t change the FROM address on emails sent from Outlook Web Access.


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