You can open the shared mailbox. You can read every email in it. You hit Reply on a customer's question, type the answer, press Send, and a minute later a bounce lands in your own inbox telling you that you don't have permission to send as that address.
Being able to see a shared mailbox and being able to send from it are two separate permissions, and admins grant the first one far more often than the second. This page covers how to send email from a shared mailbox in every Outlook client and in Gmail, what to ask IT for so it works the first time, what the failures usually mean, and why the reply you just sent is now sitting in your own Sent Items where nobody else on the team can see it. Every click path Microsoft and Google document was checked against their current pages in October 2026, and where they don't document one, we say so.
If the shared mailbox doesn't show up in Outlook at all yet, start with getting the shared mailbox into Outlook in the first place and come back.
The short version
- Opening the mailbox isn't enough. Full Access lets you read it. To send from it you also need Send As or Send on Behalf, and only an admin can grant either one.
- To send, select From in the message and pick the shared address. The first time, you usually have to type it in: Other email address in desktop Outlook, Remove and retype on the web.
- A fresh permission isn't instant. Microsoft's general note on mailbox permissions allows up to 60 minutes, so a bounce straight after the grant isn't proof that anything is wrong.
- Your sent copy goes to your own Sent Items by default, not the shared mailbox's. An admin can change that with one setting per mailbox, and it's the only fix that works in new Outlook.
- In Gmail, each person adds the team address under Send mail as, and the reply-to defaults to their own address unless they change it.
Get the permission first: which one, and who grants it
Microsoft's guide to creating a shared mailbox says it plainly: "a user with Full Access permission can't send email from the shared mailbox unless they also have Send As or Send on Behalf permission." Full Access is the permission most people get when they're added to a shared mailbox, so they can read everything and send nothing.
The two sending permissions differ in what the customer sees:
| Permission | What it lets you do | What the recipient sees |
|---|---|---|
| Full Access | Open, read and manage the mailbox | Nothing, because you can't send with this alone |
| Send As | Send as the mailbox | Only the shared address. Microsoft: "There's no indication that the message was sent by the delegate." |
| Send on Behalf | Send for the mailbox, with your name attached | Both names, in Microsoft's example "John on behalf of Reception Building 32" |
For a support or billing address, you almost always want Send As. Send on Behalf puts an individual employee's name in front of every customer, which is fine for an assistant writing for a named manager and odd for support@. It doesn't send the customer's answer to you personally, though: Microsoft says that with Send on Behalf, "replies to these messages are sent to the mailbox or group, not to the delegate." If you have both, Microsoft's reference on recipient permissions settles it: "If a user has both Send as and Send on behalf permissions to a mailbox or group, the Send as permission is always used." Those permissions sit alongside delegate access and Full Access in a bigger family, and the full set of mailbox permissions and who can grant each has its own page.
How your admin grants it
In the Microsoft 365 admin center, Microsoft's shared mailbox configuration guide starts at Teams & groups > Shared mailboxes, then has the admin select the mailbox and, under Manage mailbox permissions, pick a permission and add the people. In the Exchange admin center it's Recipients > Mailboxes, select the mailbox, select Edit, then under Mailbox permissions select Manage mailbox delegation.
Send on Behalf is where Microsoft contradicts itself. The create-a-shared-mailbox page says "You can use the EAC to grant Send on Behalf permissions." Microsoft's Exchange Online shared mailbox page says the opposite: "You can't use the EAC to grant Send on Behalf permissions, you must use Set-Mailbox cmdlet with the GrantSendonBehalf parameter." The recipient-permissions reference agrees with the second one. If your admin can't find the option, they're not doing anything wrong. PowerShell works either way:
# Send As
Add-RecipientPermission -Identity "support@yourcompany.com" -Trustee "jamie@yourcompany.com" -AccessRights SendAs
# Send on Behalf (the @{Add=...} form keeps the people who already have it)
Set-Mailbox "support@yourcompany.com" -GrantSendOnBehalfTo @{Add="jamie@yourcompany.com"}
The comment on the second line matters. Microsoft's reference also shows a form that sets the list outright and describes it as "Replace existing delegates", so an admin who passes a bare address instead of the @{Add=...} form can quietly remove everyone else's permission.
What to send IT
Most of the back and forth comes from asking for "access to the shared mailbox" and getting exactly that. A request that gets it right in one go:
Hi, could you set me up on the support@yourcompany.com shared mailbox? I need Full Access so I can open it, and Send As so my replies go out from the support address. While you're in there, could you turn on both Sent items options for that mailbox, so replies sent from it are saved in the shared mailbox's Sent Items and the rest of the team can see them? Thanks!
Swap Send As for Send on Behalf if you do want your name on the messages. The Sent items part is explained further down.
Every client at a glance
| Client | Where the From switch is | First time you send | The catch |
|---|---|---|---|
| New Outlook for Windows | Options > Show From | From > Other email address, type the shared address | The mailbox lives under Shared with me |
| Classic Outlook ("old Outlook") | Options > From | From > Other email address | Sending fails if the mailbox is hidden from the address list |
| Outlook on the web | ... (More actions) > Show From | Right-click the From address, Remove, type the shared address | You have to start from a reply or a new message in the shared mailbox |
| Outlook for Mac | From field, once the mailbox is added | Nothing extra | The address is added to From automatically, permission or not |
| Outlook on iPhone and Android | Not documented by Microsoft | Add it via Add Account > Add a Shared Mailbox | Exchange Online only |
| Gmail | From field after Send mail as is set up | Verify the address once per person | Replies go to your own address unless you change reply-to (see below) |
Send from a shared mailbox in new Outlook for Windows
Microsoft's page on opening and using a shared mailbox in Outlook has the steps under its New Outlook tab:
- Select Mail in the navigation pane, then on the Home tab select New > Mail.
- If you don't see a From field next to Send, go to the Options tab and select Show From.
- Select From and change it to the shared address. If it isn't listed, choose Other email address and type it in.
You only type it once. Microsoft: "From now on when you want to send a message from your shared mailbox, the address will be available in your From drop down list."
When you reply to a message inside the shared mailbox (it sits in the folder pane under Shared with me), the shared address should already be in From. If it isn't, open the From dropdown and pick it.
Send from a shared mailbox in classic Outlook
If you've seen "old Outlook" in a help request, this is the one: the classic desktop app, which Microsoft now labels classic Outlook. The steps are almost the same as in new Outlook:
- Choose New Email.
- If the From field isn't at the top of the message, choose Options > From.
- Select From, change it to the shared address, and if it isn't listed choose Other email address, type it in and choose OK.
Replies work as in new Outlook: open the message in the shared mailbox, hit Reply, and check From before you send. If it shows your own name, change it from the dropdown.
Send from a shared mailbox in Outlook on the web
The web version makes you add the address to the dropdown once, and the way you do it isn't obvious. From Microsoft's Outlook on the web tab:
- Go to your shared mailbox and open a message that was sent to the shared address.
- Select Reply.
- At the top of the message, open the ... (More actions) menu and choose Show From.
- Right-click the address in From and choose Remove.
- Type the shared address and send.
After that, "the next time you reply from the shared mailbox, its address will appear as an option in the From drop-down list." New messages work the same way: show From, remove your own address, type the shared one.
If you'd rather work in the shared mailbox on its own, Outlook on the web can open it in a separate window: select your name in the navigation bar, choose Open another mailbox, type the address and select Open. A typo gives you "No match was found", which is a spelling problem and not a permission one.
Outlook for Mac: the From field can't be trusted
On a Mac you add the shared mailbox by hand, either through Tools > Accounts, selecting your account, then Delegation and Sharing > Shared With Me > +, or through File > Open > Shared Mailbox. Microsoft's Mac page then explains what that does to your From field: "the shared mailbox account is added as an option in the From field when you compose emails. This lets you select the account in the From field regardless of whether you have permissions to send from this account. If you do not have "Send As" or "Send On Behalf of" permissions for the account, email from the account will not be sent."
You can type an address you have no right to use into From in any Outlook client. The Mac is different because it puts the shared address there for you as soon as the mailbox is added, so seeing it in the dropdown tells you nothing about whether you're allowed to send as it.
Two more lines from the same page are worth knowing. "Outlook for Mac does not support Auto-mapping of shared mailboxes", so it never appears on its own. And "Outlook for Mac currently supports only Full Access permissions for shared mailboxes. While you may able to add a shared mailbox with different permissions in certain scenarios, this configuration may not be fully supported." That's about the permission the mailbox is added with, and you still need Send As or Send on Behalf on top of it to send. If the shared mailbox was set up for you some other way and it misbehaves only on the Mac, that line is the one to show your admin.
Outlook on iPhone and Android
Microsoft's page on adding a shared mailbox to Outlook mobile covers getting it into the app: tap Add Account in the left navigation pane, then Add a Shared Mailbox, and pick the account that has the permission if you have several. It only works when your mailbox and the shared one are both in Exchange Online.
What that page doesn't document is how to choose the From address when you write a new message, so we won't make up the taps. Microsoft's Outlook for iOS and Android FAQ doesn't fill the gap either. Its answer on shared mailboxes says nothing about sending, and the only sending line on that page, "Granting SendAs or Send on Behalf of permissions also allows the user to send messages as the other person's mailbox", sits in the answer about delegate mailboxes, not shared ones. It's reasonable to expect the same permissions to matter in the app, but Microsoft doesn't say so for shared mailboxes. If the app won't cooperate, Outlook on the web in your phone's browser follows the steps in the web section above.
Gmail and Google Workspace: sending as a team address
Gmail has no shared mailbox object. The team address is usually a Google Group or an alias, and each person adds it to their own Gmail so it shows up in From. Google's page on sending from a different address or alias gives the path: Settings > See all settings > Accounts and import (or Accounts) > Send mail as > Add another email address.
If the address is a Google Group, the verification email goes to the group rather than to anyone's inbox, and Google has a separate procedure for confirming it. The full verification walk-through for a Google Group address covers those five steps, including the one setting you need to put back afterwards. What that page doesn't cover:
- Replies can come back to you, not the team. Google's page says that "When you send a message, replies will go to your original Gmail address by default", and its fix is under Send mail as: Edit info > Specify a different "reply to" address > Save Changes. Do it on the team address's entry and enter the team address as the reply-to, or the customer's next message can bypass the shared address entirely. Send one test message to yourself and hit Reply on it before you trust it.
- There's a cap. "You can send emails from up to 99 different email addresses."
- A personal Gmail account sending as another domain can show both addresses. For that case, Google warns that recipients using Outlook or another mail service "might see something like, "From yourname@gmail.com on behalf of othername@otherdomain.com"." A Workspace account sending as a group on its own domain is the normal team setup, and it isn't what that warning describes.
If you're sending from a delegated Gmail account instead, the rules change. Google's delegation help page says that "When a delegate sends a message from your account, their email address appears", and that "It can take up to 24 hours before a delegate can use your account." Whether recipients see the delegate is set by your Workspace admin. Google's admin setting for delegation offers two defaults: "Show the account owner and the delegate who sent the email", or "Show the account owner only", where "The delegate email address is not included." That's Gmail's version of the Send on Behalf vs Send As choice. The admin sets the default, and can also tick "Allow users to customize this setting" to hand the choice to each account owner.
Can't send from the shared mailbox? Work through this
Go in this order. It runs from the most common cause to the least obvious one.
1. Check which permission you actually have. If you were only given Full Access, nothing you do in Outlook will let you send, and the bounce or error will tell you, in one wording or another, that you don't have permission to send as or on behalf of the mailbox. Microsoft documents one version in a troubleshooting article for on-premises Exchange Server, where someone with Full Access and Send on Behalf sends through a separate Outlook profile for the shared mailbox and gets "You do not have the permission to send the message on behalf of the specified user." Microsoft's resolution there is to "Grant Send As permission to the user for the shared mailbox." Microsoft 365 may word its bounce differently, but the first question is the same: do you have Send As, or only Full Access?
2. Give a new permission time. Microsoft's admin note on mailbox permissions says that "it can take up to 60 minutes for the changes to propagate through the system and be in effect." That page is written about user mailboxes, and the shared-mailbox pages don't give a figure, so treat an hour as a sensible wait rather than a promise. Restart Outlook after it and try again before you open a second ticket.
3. Ask whether the mailbox is hidden from the address list. Admins sometimes hide a shared mailbox from the address list to keep it out of everyone's address book. Microsoft documents what that does twice, with different scope. The create-a-shared-mailbox page says Send As and Send on Behalf "do not work in the Outlook desktop client with the HiddenFromAddressListsEnabled parameter on the mailbox set to True, since they require the mailbox to be visible in Outlook via the Global Address List." The recipient-permissions reference has no client qualifier at all: "If you assign the Send As permission to a mailbox that is hidden from address lists, the delegate won't be able to send messages from the mailbox." Your admin can see this setting and you can't, so ask about it whatever client you use, and first of all if sending fails in desktop Outlook.
4. On a Mac, ignore the dropdown. As above, the address appears whether or not you can send from it. Confirm the permission with your admin instead of trusting the client.
5. Check From before every send. If the message went out fine but from the wrong address, nothing failed. From defaulted to your own address. On the web in particular, the dropdown only remembers the shared address after you've used it once.
Shared mailbox sent items: why your reply is in your own folder
This one isn't an error. It's the default, and Microsoft's configuration guide says so: "By default, messages sent from the shared mailbox aren't saved to the Sent Items folder of the shared mailbox. Instead, they are saved to the Sent Items folder of the person who sent the message." The reason, from Microsoft's article on why sent mail isn't saved to the shared mailbox, is that "You can't sign in to a shared mailbox. Instead, you sign in to your own mailbox, and then you open the shared mailbox."
For a team, that default is a real problem. Your colleague opens the shared Sent Items to see whether the customer already got an answer, finds nothing, and answers again.
The fix is on the mailbox, so your admin does it once for everyone:
- In the admin center: open the shared mailbox, "Select Edit under Sent items", and "Select the options you want for sent items". Microsoft doesn't spell the options out on that page. Cover both kinds of send, Send As and Send on Behalf, which are the two settings in the PowerShell below.
- In PowerShell:
Set-Mailbox "support@yourcompany.com" -MessageCopyForSentAsEnabled $True
Set-Mailbox "support@yourcompany.com" -MessageCopyForSendOnBehalfEnabled $True
Both are off by default. To check the current state, Get-Mailbox "support@yourcompany.com" | Format-List MessageCopyForSentAsEnabled,MessageCopyForSendOnBehalfEnabled shows both values.
Turning this on doesn't take the copy out of your own Sent Items. With the default client settings, Microsoft says "A copy of the email will be saved in both the primary mailbox and the shared mailbox." There's also an older per-machine registry fix, which doesn't work in new Outlook and can combine with this setting into duplicate copies. How the registry setting interacts with the mailbox setting has Microsoft's combination table, if anyone on your team is tempted.
Where sending from a shared mailbox runs out
Once the permissions are right and the Sent items copy is on, the mailbox does what it was built to do. Everyone can reply as support@, and everyone can see what was sent.
What it still can't tell you is who's dealing with a message right now. Two people can open the same customer email within a minute of each other, and nothing in the shared mailbox shows that one of them has already started. The shared Sent Items will show that the customer got two answers, but only after both have gone out. The usual workarounds are flags, categories and a channel where people post "I've got this one". They work about as well as you'd expect once there are more than three of you.
That's the gap between a shared mailbox and a shared inbox, and what a shared inbox adds on top of a shared mailbox is the longer answer. A shared inbox tool like TriageFlow assigns each incoming email to one person based on how your team is set up, and keeps internal comments on the conversation itself instead of in a side chat. It works with any email provider, not only Microsoft 365 or Gmail.
Frequently asked questions
Why can't I send an email from a shared mailbox?
Most often you were given Full Access, which opens the mailbox but can't send from it. Ask for Send As. If you already have it, the grant may be too new, or the mailbox may be hidden from the address list. The troubleshooting list above goes through both.
How do I get permission to send from a shared mailbox?
Ask your Microsoft 365 admin. You can't grant it to yourself, and the owner of a shared mailbox can't either, because nobody owns one. Ask for Send As by name. "Access to the mailbox" usually gets you Full Access and nothing more.
How do I send from a shared mailbox in old Outlook?
Choose Options > From in a new email, then pick the address under From. The first time it won't be listed, so use Other email address and type it in.
Will customers see my name when I send from a shared mailbox?
Only if you were given Send on Behalf, which shows your name on behalf of the mailbox. Send As shows just the shared address, and if you have both, Send As wins. Either way, the customer's reply goes to the mailbox, not to you.
Why are emails I send from the shared mailbox in my own Sent Items?
Microsoft 365 files the copy with whoever pressed Send, because that's the account that's signed in. A setting on the shared mailbox, changed once by an admin, puts a copy in the shared Sent Items too. Nothing you change on your own machine fixes it in new Outlook.
Can I send from a shared mailbox on my phone?
You can add it to the Outlook app if both mailboxes live in Exchange Online. Sending from it is the undocumented part, so if the app doesn't offer the address, Outlook on the web in your phone's browser is the route Microsoft does document.
Bottom line
If you're the person who sets these mailboxes up, most of the tickets above never have to happen. Grant Full Access and Send As together, to each person directly, at the moment you add them. Turn on the Sent items copy when you create the mailbox, not after the first double reply. Think twice before hiding a mailbox people need to send from. And when someone reports that a reply went out under their own name, check their From field before you check their permissions, because that's usually the whole fix.