Send on Behalf in Outlook: A Guide to Email Delegation

When a sales director receives dozens of emails a day, it is perfectly normal for an assistant to reply for them, book meetings or send quotes. The point is to do it clearly: whoever receives the message should understand who wrote it and on whose behalf.

Outlook and Microsoft Exchange provide the Send on Behalf permission for exactly this. It takes a few minutes to enable, but a few less visible settings make the difference between tidy delegation and a source of confusion. In this guide we cover:

• the difference between “Send on Behalf” and “Send As”;
• how to enable delegation, as a user and as an administrator;
• how to send an email on behalf of a colleague;
• the most common issues and how to fix them.

Send on Behalf, Send As, Full Access

Before configuring anything, it pays to pick the right permission. There are three, and they are often confused.

Permission	What the recipient sees	When to use it
Send on Behalf	“Delegate on behalf of Owner”	Transparent delegation: executive assistants, sales coordinators
Send As	The owner’s name only	Department mailboxes such as info@ or support@
Full Access	Does not allow sending on its own	Reading and managing someone else’s mailbox

With Send on Behalf, both identities stay visible: the “From” line shows the person writing alongside the mailbox owner. Recipients know who they are dealing with, and the writer takes responsibility for the message.

Send As hides the delegate completely: the message looks as if the owner wrote it. It is useful for department mailboxes, where the address matters more than the person, and far less so when writing on behalf of a specific individual.

Full Access lets you open someone else’s mailbox, but not send from it: to write, you also need one of the two permissions above.

How to enable delegation

There are two routes: the mailbox owner sets it up in Outlook, or an administrator does it for one or more users.

In classic Outlook for Windows (mailbox owner)

1. Open Outlook and go to File > Info > Account Settings > Delegate Access.
2. Click Add, search for your colleague’s name and confirm.
3. In the permissions dialog, choose the access level for each folder. If your colleague only needs to send, set Calendar, Inbox and the other folders to None.
4. Tick the option that sends the delegate copies of meeting-related messages only if they also need to manage your appointments.
5. Click OK to save.

Adding a delegate already grants the Send on Behalf permission. Setting folders to None is the detail many people overlook, yet it is the most important one: your colleague can write on your behalf without seeing emails and appointments they do not need. It is the principle of least privilege, which also helps with GDPR because it limits access to the personal data held in the mailbox.

As an administrator

Anyone managing mailboxes for several users does it from the admin console. In Microsoft 365 the path is Users > Active users: select the owner and, on the Mail tab, open the mailbox permissions (Send on behalf).

For many users at once, use Exchange PowerShell. Watch out for one detail: with a plain address, the command replaces the list of delegates; to add one without removing the others, write it like this:

Set-Mailbox -Identity "management@example.com" -GrantSendOnBehalfTo @{Add="assistant@example.com"}

If your email runs on EagleMercury Hosted Exchange, mailboxes are managed from the same EagleMercury console, integrated with the accounts your company already has.

How to send an email on behalf of a colleague

Once the permission is in place, sending takes a few clicks. The process differs only slightly between Outlook for Windows and Outlook on the web.

Classic Outlook for Windows

1. Open a new message and go to the Options tab.
2. Click From to show the sender field.
3. From the From drop-down, choose Other Email Address and look up the owner’s name in the Global Address List.
4. Write and send as usual.

Outlook on the web

1. Open a new message and, from the Options tab or the … menu, choose Show From.
2. Click the From field and select the owner’s address.
3. Write and send.

The recipient will see the sender as “Delegate Name on behalf of Owner Name”. Menu labels may vary slightly between Outlook versions.

One thing to check first: the owner’s mailbox must be visible in the Global Address List. If it is hidden, the delegate cannot select it, whichever app they use.

The most common issues

Even with everything set up correctly, a few snags can occur. These are the most frequent:

• The permission does not seem to work. Changes are not always immediate: they can take anything from a few minutes to a few hours. Try again later before asking for help.
• Messages do not appear in the owner’s Sent Items. By default they go to the delegate’s Sent Items. An administrator can have a copy saved in the owner’s mailbox as well (the -MessageCopyForSendOnBehalfEnabled $true parameter of Set-Mailbox).
• The From button is missing. In Outlook for Windows the field stays hidden until you enable it from the Options tab; after that it remains visible in new messages.
• A “You do not have the permission” error. Usually the delegation was not saved, or the wrong address was chosen in the From field. Ask the owner to grant access again and check the selected sender.

Delegation and security

Delegation is also a matter of control. A few good habits:

• Review delegations regularly and remove them as soon as a colleague changes role or leaves the company.
• Prefer Send on Behalf to Send As when writing on behalf of a person: recipients learn to recognize who is writing, and “from the boss” messages are exactly what fraudsters imitate.
• Protect your email against impersonation. Fraud that pretends to come from an executive is among the most widespread. In EagleMercury Hosted Exchange, Email Protection Premium includes AI Guardian, which detects executive and vendor impersonation as well as invoice and payment fraud.

In short

• Send on Behalf shows both the writer and the owner: it is the right choice for assistants and executive support.
• The owner enables it in Outlook (Delegate Access), the administrator from the console or with PowerShell; setting folders to None limits access to what is actually needed.
• To send, simply show the From field and pick the owner from the Global Address List.

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