Send As vs. Send on Behalf: Which Should You Use?

Send As vs. Send on Behalf: Which Should You Use?

Send As vs. Send on Behalf: Which Should You Use?

Overview

Microsoft 365 offers two ways to send mail from someone else's mailbox or a shared mailbox: Send As and Send on Behalf. They look similar at first, but recipients see them differently and they are used for different purposes. This guide explains the difference so you can request the right permission.

Before You Begin

  • You need permission to either send method. Your administrator grants this — you cannot self-assign it.
  • Know what the mailbox is used for (a shared role like support@, or a person's individual mailbox).

The Difference at a Glance

Send As

  • Recipients see the message as if it came directly from the shared mailbox.
  • From shows: support@yourcompany.com
  • No mention of who actually sent it.
  • Best for shared role mailboxes (support, billing, info) where the team identity matters more than the individual.

Send on Behalf

  • Recipients see both the sender and the mailbox owner.
  • From shows: Your Name on behalf of support@yourcompany.com
  • Transparent about who composed the message.
  • Best for executive assistants sending for an executive, or any case where accountability matters.

When to Pick Each

Pick Send As when:

  • The mailbox represents a team or function (support, sales, info).
  • You do not want clients to know which team member responded.
  • The reply needs to go back to the shared mailbox.

Pick Send on Behalf when:

  • You are sending for a specific person, like an executive.
  • The recipient needs to know a human composed the message.
  • You want the reply to go to the executive directly, not to your inbox.

How to Request the Right Permission

  1. Decide which style fits your workflow.
  2. Submit a ticket and include the mailbox address and which permission you need.
  3. We will confirm with the mailbox owner before granting access.

Troubleshooting

  • If you already have one permission and need to switch: submit a ticket. Holding both Send As and Send on Behalf at the same time can cause inconsistent behavior — pick one.
  • If recipients see "on behalf of" when you expected Send As: your permission may be Send on Behalf, not Send As. Check with your administrator.
  • If Outlook still uses your address instead of the shared one: see the article Send Email From a Shared Mailbox for how to change the From field.

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Need More Help?

Submit a ticket at support.bostonmit.com or email support@bostonmit.com.

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