Microsoft 365 Group vs Shared Mailbox vs Teams Channel: Which One a Customer Can Actually Write To

A shared mailbox is the only one of the three where a customer’s email arrives and the reply goes back out from the very same address. A Microsoft 365 group takes outside mail once a switch is turned on, and its members mostly answer as themselves. A Teams channel receives email and cannot reply to it at all, which Microsoft says in one sentence on its own support page and which nobody choosing between the three has generally read.

That is the whole page in a paragraph, and the rest of it is the documentation behind each part of that, with the dates it was pulled, so you can check the lot of it your own self.

Over here at Maxdesk we sell a help desk, the thing people buy after the three rooms below stop holding, so the person writing this has a stake in where you land, no two ways about it. Fair is fair though, two of the three verdicts further down come to stay where you are, and a good deal of what follows is Microsoft’s furniture rather than ours.

What the three are underneath, since one of them is the other one

Start with the part that makes the comparison a bit false before it begins. Microsoft Teams uses Microsoft 365 Groups for membership, which is Microsoft’s own sentence, and what it means is that every team you have ever made is a group already, with a group mailbox sitting behind it that most people have never once opened. Teams against a group is not a choice between two things at all. It is a choice between two doors into the one room, and the question that matters for a support address is which door you hand to a stranger.

A shared mailbox is a mailbox with a disabled account under it, opened by several licensed people inside your organisation, answering as the shared address. One copy of each mail, one place, and replies out as support@ rather than as a person. That is the whole of it and we have gone through its own five stops in the piece on the Outlook shared mailbox, so none of that is repeated here beyond a table row.

Then the Microsoft 365 group, which is a membership object with furniture attached, a group mailbox, a SharePoint library, a calendar, Planner, and a team if somebody made it from Teams. Mail sent to the group’s address lands in the group mailbox. Nobody is stopping it. Members can subscribe to get copies in their own inbox, or not, and which of those is the default turns out to matter enormously, so it gets its own section below.

The Teams channel email address is a third thing again, mind you, and it is the one people are most surprised by, on account of it looking so much like an inbox. Every standard channel can be given an address, it looks like a long string of letters at a Microsoft domain, and anything mailed to it appears in the channel as a post with the attachments filed in SharePoint. The post sits inside Teams and the customer is stood outside it, and that turns out to be the whole of it, mind you.

What Microsoft documents about each of them

Every figure in this table came off Microsoft’s own documentation on 21 September 2026, across seven pages that are named at the end of this piece. Read the three columns and notice that the row that decides a support desk is not any of the big numbers, it is the one about the reply.

The temptation reading that is to go straight to the storage row, since 50 GB looks like the number that ends things. It is not. Two rows do the deciding on a support desk, and they are the second and the third, and the next two sections are those two rows written out at length.

Why a Teams channel can take a customer’s email and never answer it

Here is the sentence, straight from Microsoft’s support page on sending email to a channel. Replying to the post in Teams doesn’t send an email reply to the original sender. Any comments or conversations you have about the email in a channel aren’t visible outside of Teams.

Sit with that a minute, on account of what it does to the arrangement a lot of desks have gone and quietly built for their own selves. Somebody found the Get email address option on a channel, gave that address to a supplier or put it on a form, and now every message that comes in appears as a post with the team’s name over it. It looks like an inbox. People reply to it the way they would reply to anything else in Teams, underneath the post, and the reply is a very good reply, mind you, and the customer never sees a word of it. Nothing bounces either. The customer simply hears nothing. That goes on for as long as it takes them to ring.

It is not a defect, to be honest with you, and Microsoft never once claimed the channel address was a mailbox. It is a way of getting an email into a conversation your team is already having, and for that it is grand. A vendor’s invoice landing in the finance channel, an alert from a monitoring tool, a CSV export somebody mails in each Friday, a newsletter the whole team reads. It runs the one way. Where it goes wrong is the day somebody outside the company is on the other end of it, waiting.

There are smaller stops on the same door and they are worth having in one place. The address is a plain SMTP address, so anything that can send mail can reach it, IMAP clients, a scanner, a form on a website, one and all. The address has to be turned on by your IT admin first, under email integration in the Teams org-wide settings, and an admin can limit it to listed SMTP domains, which is the right thing for them to do and the thing that silently drops a new customer’s domain. The body of the mail is capped at 24 KB. So a message with a quoted thread underneath it arrives as a preview and a link to download the original, which is the very same experience as an attachment. The address cannot be put inside a distribution list, the mail fails if it is. The attachments land in SharePoint with a unique ID stuck on the end of each file name, so a customer’s invoice-march.pdf is no longer called that when you go looking. And on the government plans, GCC and above, the whole feature is not there at all.

Which door an outside sender can knock on by default

Say the customer writes to the address on your website at half nine on a Monday and nothing arrives anywhere. Which of the three it is decides where you go looking.

On a shared mailbox the mail arrives if the admin allowed external senders. Most did at setup, since a support address that only staff can write to is not much of a support address. So that one is usually the customer’s own typo, truth be told. Check the spelling first.

With a Microsoft 365 group the mail is rejected unless somebody went and turned on the setting called Let people outside the organization email this group, which sits on the group’s settings tab in the admin centre and which Microsoft’s own documentation illustrates with info@contoso.com, on account of that being the obvious use for it. The documentation also says it may take up to 30 minutes before outside people can write in after you turn it on, which is the half hour in which somebody tests it, sees it fail, and concludes it does not work. So a group that was set up as a project room and then handed a public address will bounce the public until that switch is thrown, and the bounce goes to the customer, not to you.

Teams channel next. The mail arrives if the admin turned email integration on and the sender’s domain is on the list, if there is a list, and then it becomes a post, and then the section above happens to it.

Three doors, three different failures, and only one of the lot tells you it failed. A missing email that comes down to “check the switch” means you are on a group. Teams is the one where it came in and you replied and they never got a word of it, and you only find that out from them. And the bounce nobody on the desk can find at all is usually the shared mailbox gone full, which is a separate story and one we have told elsewhere.

Where the group’s mail goes when nobody is subscribed

Fair is fair, the group does one thing here that neither of the others can. The group mailbox keeps every conversation, and only the owners can delete from it, which is more than the shared mailbox can offer, since Microsoft’s own page on shared mailboxes says outright that deletion by members cannot be prevented there, and points you at a group if you need it prevented. On a support address a deleted mail is a customer nobody answered, so a room where only two or three named people can do the deleting is a genuinely better room, all the same.

The trouble is who is in it. When you use the admin centre to create a group, by default the members do not get copies of group emails sent to their inboxes. They will need to go to the group to see conversations. That is Microsoft’s own description of the default, not our paraphrase of it, and it is the mechanism behind a thing we argued elsewhere without the citation, that a group is a room people must remember to visit. That argument is written out in full where we set the shared mailbox against a distribution list, and it is not getting a second run here. What that page did not have was the sentence above, and the sentence is the whole of it. A customer’s question in a group is waiting for somebody to walk in, and the default is that nobody is told to.

You can turn copies on, in the very same settings tab, and then every member gets each mail in their own inbox and can delete their copy without touching the group’s. That goes and fixes the walking-in problem and hands you a different one. A desk of six now has six copies of each customer mail plus the master, and two of the six answer it from their own inbox, as their own selves, because send as on a group is a permission an admin must grant separately and almost never has. The customer gets two replies from two people and writes back to one of them. The thread has left the group. Nobody noticed it go. Which is more or less where the distribution list story started, and it is the reason the group is the right room for a team’s own conversation and the wrong one for a stranger’s.

How the sizes compare, and why the small one bites first

Numbers now, and the shape of them is not what you would guess from the table, funnily enough.

Take an ordinary support mail. A customer replies to a thread that has gone back and forth four times, with three phone photographs of a damaged part attached, each about 4 MB. Into a shared mailbox that is nothing. The default send ceiling on Exchange is 35 MB and the message is 12 MB with the pictures. It arrives whole, thread and all, and anybody with access opens it as they would any other mail.

Into a Teams channel the very same message hits two ceilings at once. The pictures are fine, each under 10 MB and there are only 3 of them against a limit of 20. It is the body that fails. Every time. Four rounds of quoted thread is a good deal more than 24 KB of text, so what appears in the channel is a preview and a link asking somebody to download and view the original email. The person who clicks the link is now reading an .eml file in a browser tab, and the photographs are sitting in a SharePoint folder under file names with an ID on the end that no longer match what the customer called them. All of it is documented, none of it is news to Microsoft, and the desk finds out about it on the afternoon the customer rings.

The group is the same as the mailbox on this row, since a group mailbox is an Exchange Online mailbox and the same 35 MB default applies, and the 50 GB on the group mailbox is the same 50 GB as the shared one. Where the sizes differ between those two is not the mail at all but the files, 1 TB plus 10 GB for every subscribed user on the group’s SharePoint side, which is a great deal of room and is room for documents rather than for customer correspondence.

One more figure on the shared mailbox that the group quietly changes. The shared mailbox stops at 25 users, Microsoft’s figure, and their own advice past that is a Microsoft 365 group, and the group will take more than 1,000, with 1,000 of them on the conversations at one time. That is a real answer to a real ceiling, no two ways about it. It is also the third time on one Microsoft page that the group is offered as the exit from the shared mailbox, the other two being outside people and deletion. Every one of the three exits costs you the reply going out as the address, unless an admin goes and grants send as afterwards, which is the step that gets missed.

When Teams is genuinely the right desk

There is a desk for which all of the above is fine, and it is the one where the person asking is already inside Teams.

An internal IT desk, a facilities desk, HR questions from staff. Somebody in accounts posts in the IT channel that the printer on the second floor is doing the thing again, three people see it as a post, one of them replies underneath, and the reply reaches her, since she is a member and she lives in Teams all day the very same as the rest of them. No email in the loop at all. The channel address is not even needed. It works. Nobody outside the building is waiting for anything, and the one-way door does not matter when everybody is already on the same side of it.

It stays fine for a good long while. Where it stops is the day somebody asks how many printer requests came in last quarter and how long each waited, at which point a channel is a scroll and not a record, and the honest tool for that question is an IT ticketing system with a queue and a clock, which can still take its requests out of Teams if people would sooner ask there. But that is a growing-up problem and not a wrong-door problem. Teams for staff-facing requests is a perfectly good place to begin.

The customer-facing desk is the one that must not be in a channel, and the reason is the one sentence up the page. A customer is not a member. They see neither the post nor the reply underneath it, and Teams has no way of carrying the reply back out to them, nor was it ever meant to.

What to set up on day one, whichever of the three you keep

Six things, most of them a minute each, and they are the ones that go and catch desks out on the day it matters.

1. On a shared mailbox, confirm external senders are allowed and that Send As is granted to everybody who will answer, so replies leave as the address and not as a person.
2. On a Microsoft 365 group carrying a public address, turn on Let people outside the organization email this group, then wait the documented 30 minutes before testing it from a personal account.
3. On that same group, decide the copies question on purpose. Either turn on Send copies of group conversations and events to group members and have an admin grant send as, or leave copies off and put one named person on visiting the group each morning. Leaving it on the default is choosing nobody.
4. On a Teams channel that receives email, write on the channel itself that replies underneath a mailed post do not reach the sender, and give the channel a rule for who takes an outside mail into Outlook and answers it from there.
5. Ask your admin whether email integration is limited to listed SMTP domains, and if it is, know that a new customer’s domain is not on it.
6. Whichever you keep, put a re-check in the calendar twice a year against the storage figure and the user count, since none of the three warns you before it fills or before the twenty-sixth person joins.

The third one is the one to do today. Not tomorrow. A group left on its defaults, with a public address on it, is an address that nobody has been told to read.

Two of the three verdicts cost nothing

Keep the group for what it was built for, which is a team talking to its self around its own files and calendar, the lot of them in the one room. A project, a department, a committee. It is the best room Microsoft makes for that, and a new member scrolling back through two years of it is a real thing to have. Do not hand it a public address unless you have gone through item three above on purpose.

The Teams channel stays for requests from people who are already in Teams. Staff asking IT for things, facilities, the kind of desk where the requester and the answerer are both members. Give the channel an email address for the vendor alerts and the monitoring tool, and for nothing that expects a reply.

Put the customer-facing address on the shared mailbox if it is anywhere else today, and do it this week. For a desk of two or three at ordinary volume that is the whole of the fix, and it costs you nothing beyond the licences you already hold. Where it stops is written up separately, and the day it stops has little to do with size. It is the day handovers start dropping, and the whole of that argument lives in our piece on when a shared inbox becomes a ticketing system. Over on Google Workspace the same three-way reads differently again, and the Google Collaborative Inbox piece covers that one, Google Groups and all.

The thing we make, and the bill for it

Maxdesk is a help desk that takes whichever address you already have and puts the layer on top that none of the three rooms above has got. You forward support@ into a workspace, from the shared mailbox or the group, and what arrives has an owner, a status and a clock on it, with an SLA policy on it, which out of the box wants a first reply inside 1 hour and a resolution inside 8, both of them yours to change. The shared inbox view keeps the one-copy-one-place virtue of the mailbox and adds the names. Automation rules tag and route without a person watching, and every reply goes back out to the customer from the address they wrote to, which after the last two thousand words is the row in the table we would want to be judged on.

The bill goes by the workspace. There is a free tier, and it does not count agents or tickets beyond a fair-usage line, and two paid tiers sit above it, and none of the three counts how many of you are on it, so the twenty-sixth person costs the very same as the fourth. The free tier carries ads in the workspace, puts our name on outgoing mail, and keeps a 3-month rolling history, which are three trades a shared mailbox never asks of you and we would rather say so here than have you find them on the pricing page.

The parts of this we would argue with ourselves

We have no Teams app. Said plainly, so nobody reads this page and expects one: there is no Maxdesk tab in Teams, no bot that turns a channel post into a ticket, and no sync back the other way. If your staff want to ask for things in Teams and have those become tickets, that is a gap with us today, plainly said, and there is no point pretending otherwise. Mail is the one channel we have built, which means the internal IT desk described above, the one that genuinely works in a channel, is one we serve only once the request arrives as a mail.

Nor is there any migration tooling. Nothing lifts the history out of a group mailbox or a shared mailbox and into a workspace, and for what it is worth Microsoft says the same about its own furniture, that it is not possible to migrate a shared mailbox to a Microsoft 365 group. What most desks do is pick a Monday, begin from there, and leave the old mailbox open to read for as long as anybody wants it, and that is the honest answer for us the very same as for them. The rules and colours people build on the mailbox meanwhile are their own subject, and we went through what they can and cannot carry under shared mailbox rules.

And the figures. Every Microsoft number here came off seven of their pages on 21 September 2026, dated between May 2025 and July 2026, and vendors move these lines, the Teams limits page in particular gets revised often. Our own product facts got the same going-over on the same afternoon, and March 2027 is in the diary for doing the whole of it again. If a number on this page is the thing your decision turns on, open the Microsoft page and read it your own self before you act on it, and if the address is landing in spam on the way out, that is a different problem again, covered under keeping support@ deliverable.

Where to start, if you are not sure which door you have

Send a test. Not a plan, a test. Use a personal Gmail or whatever you have outside the company, to the support address on your website, and then watch where it goes and time how long it takes to get an answer back at the personal address.

A bounce means a group with the outside-senders switch off, or a full mailbox, and the bounce text tells you which of the two. Say it arrived somewhere and the reply you sent never reached the personal address, then go and look at the place you replied from, since a Teams post or a group conversation both look like replying and neither one of them leaves the building. A reply that did arrive, but under a person’s name rather than the support address, points at a group without send as, or a mailbox where somebody forgot to pick the From, and funnily enough the second is the commoner of the two. And if it came back promptly from the address you wrote to, your door is sound, whatever it happens to be built on, and the only remaining question is whether anybody in the building knows who owns the thread, which is a question none of the three rooms answers and the one we sell the answer to.

Common questions about Microsoft 365 groups, shared mailboxes and Teams channels

Can a Teams channel be used as a help desk email address?
It can receive email, once an IT admin turns on email integration, but Microsoft documents that replying to the post in Teams does not send an email reply to the original sender. So it works for requests from people inside Teams and not for customers outside it. The message body is also capped at 24 KB before Teams substitutes a preview and a download link.

What is the difference between a Microsoft 365 group and a shared mailbox for support?
A shared mailbox is one mailbox opened by up to 25 licensed people, with replies sent as the shared address. A Microsoft 365 group is a membership object with a group mailbox, files and a calendar; outside senders need a switch turned on, members get no copies by default, and members reply as themselves unless an admin grants send as. Only group owners can delete from the group inbox, which is the one thing it does better for a support address.

Can people outside the organisation email a Microsoft 365 group?
Yes, once the group setting Let people outside the organization email this group is turned on. Microsoft documents that it may take up to 30 minutes before outside senders can write in after the change.

Do Microsoft 365 group members get an email when something arrives?
Not by default when the group was created in the admin centre. Microsoft’s documentation says members will need to go to the group to see conversations unless the setting to send copies of group conversations to members’ inboxes is turned on.

Is a Microsoft Teams channel the same as a Microsoft 365 group?
Every team is built on a Microsoft 365 group, since Teams uses groups for membership, so a team already has a group mailbox behind it. A channel email address is a separate door that turns an incoming email into a channel post; it is not the group’s mailbox address.

Which of the three should a customer-facing support address use?
The shared mailbox, for a small desk at ordinary volume, because it is the only one of the three where the customer’s mail lands in one place and the reply returns from the address they wrote to. Move it there this week if it is on a group or a channel, and look at a help desk only on the day handovers start dropping.