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You can try these commands for the Windows Azure Powershell<br />
$LiveCred = Get-Credential<br />
<br />
$Session = New-PSSession -ConfigurationName Microsoft.Exchange -ConnectionUri <a href="https://ps.outlook.com/powershell/" rel="ugc">https://ps.outlook.com/powershell/</a>&nbsp;-Credential $LiveCred -Authentication Basic -AllowRedirection<br />
<br />
Import-PSSession $Session <br />
<br />
To verify that the permissions send mail on behalf of another user:<br />
Get-Mailbox -identity user@example.com | fl *GrantSendOnBehalfTo<br />
<br />
To remove Send On Behalf permission from a mailbox, use the following command:<br />
Set-Mailbox -Identity user@example.com -GrantSendOnBehalfTo $NULL
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As comfortjeanius suggested, you need to verify the permissions. It's easiest to do this using the EAC:<br />
<br />
<a href="http://technet.microsoft.com/en-US/library/bb123809(v=exchg.150).aspx#MailboxDelegation" rel="ugc">http://technet.microsoft.com/en-US/library/bb123809(v=exchg.150).aspx#MailboxDelegation</a>
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Ok user has send as and full permisson to the mailbox<br />
She has it added under her mailbox and she can reply and change the from to the secondary mailbox &nbsp;but when in it doesn't default to secondary.
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Well the default one is configured by setting the default account in Account settings, it will not change based on the context. If this is a normal mailbox, she can add it as separate account in Outlook and it will auto-update the send address depending on which account she is working with (on Outlook 2013 at least). <br />
<br />
If this is a shared mailbox however, the send from address will not change to it. As a workaround you can add the shared one as POP account so you can set it as the default, but again it's not an ideal solution.
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To assign &quot;Send on behalf of &quot;&nbsp;permissions<br />

<pre><code class="code-1 nolinks" id="code-20-39762655-1"><span>Set-Mailbox -Identity &lt;DisplayName A&gt;  -GrantSendOnBehalfTo &lt;DisplayName B&gt;</span>
</code></pre>
<br />
To remove &quot;Send on behalf of&quot; permissions<br />

<pre><code class="code-1 nolinks" id="code-20-39762655-2"><span>Set-Mailbox -Identity &lt;DisplayName A&gt; -GrantSendOnBehalfTo $null</span>
</code></pre>
<br />
Plus here is some information for your safe keeping <a href="http://www.o365info.com/2012/09/mailbox-permissions-powershell-commands.html#SUB-1" rel="ugc">Mailbox Permissions - PowerShell commands</a>
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@ comfortjeanius - she does not want to send on behalf, but send as<br />
<br />
@ vasilcho - ok to clarify If I have my mailbox open in Outlook and a secondary with full access and send as. &nbsp;If I am in the secondary mailbox under my account and reply it will NEVER send as that user as it is under my account?<br />
<br />
I want to make sure I'm clear as I can just change the from field and it will work, but the user would like to avoid that step and told me it used to work so want to make sure I am clear it is not possible.
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<div class="content wysiwyg-content">
We are new to Exchange Online/Office 365 and I have a user who used to be able to send email as a secondary mailbox they had access to in their Outlook and now it shows up as send on behalf. &nbsp;How can this be set back?<br />
<br />
Thanks
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We are new to Exchange Online/Office 365 and I have a user who used to be able to send email as a secondary mailbox they had access to in their Outlook and now it shows up as send on behalf.  How can this be set back?

Thanks

Exchange Online user with Office 365 cannot send mail as only on behalf

Office 365 is a group of software plus services subscriptions that provides productivity software and related services to its subscribers. Office 365 allows the use of Microsoft Office apps on Windows and OS X, provides storage space on Microsoft's cloud storage service OneDrive, and grants 60 Skype minutes per month. Office 365 includes e-mail and social networking services through hosted versions of Exchange Server, Skype for Business Server, SharePoint and Office Online, integration with Yammer, as well as access to the Office software. All of Office 365's components can be managed and configured through an online portal; users can be added manually, imported from a CSV file, or Office 365 can be set up for single sign-on with a local Active Directory using Active Directory Federation Services.

Microsoft 365

Microsoft Office is an integrated suite of applications that includes Outlook, Word, Excel, Access, PowerPoint, Visio and InfoPath, along with a number of tools to assist in making the individual components work together. Coding within and between the projects is done in Visual Basic for Applications, known as VBA.

Microsoft Office

Exchange is the server side of a collaborative application product that is part of the Microsoft Server infrastructure. Exchange's major features include email, calendaring, contacts and tasks, support for mobile and web-based access to information, and support for data storage.