Email Aliases vs Shared Mailboxes vs Extra Licences: What Does sales@ Actually Cost?

The request arrives from sales, or marketing, or whoever just designed the new flyer. “Can we have sales@ on the website?” Then it reaches whoever pays the bills and changes shape: is that another user we pay for every month?

Usually not. But the wrong answer here has a particular quality — it doesn’t cost you once, it costs a licence fee every month, forever, for an address that gets four emails a week. Do that three or four times across a decade and you carry a permanent charge for mailboxes nobody has thought about since 2019.

This is the money version of a question we covered elsewhere. If you want help choosing the right object for info@ — mailbox, list or group — read shared mailboxes vs distribution lists vs Microsoft 365 groups. This one is about what each costs.

An alias is free, and it is not a mailbox

An alias — Microsoft calls it a proxy address — is a second address attached to a mailbox that already exists. Mail sent to it lands in the same inbox as everything else. No new object, no new storage, no new bill. You can add several to one mailbox; Microsoft’s limit is high enough that a small business will never reach it.

This is the right answer more often than people expect. If Jane runs sales on her own, sales@ can be an alias on her mailbox and the job is done at no cost. The same goes for addresses on an old domain after a rebrand, the misspelling of your company name customers keep using, and the address a departed member of staff held.

The catch is direction. An alias reliably receives; it does not reliably send. Reply to a message that arrived at sales@ and it will usually go out from Jane’s own address. A setting now permits sending from an alias, but client support has been patchy and has shifted over time. So the honest rule: use an alias when mail needs to arrive somewhere, and something else when replies need to leave under that name.

A shared mailbox is also free, until it isn’t

A shared mailbox is a real mailbox with its own inbox, folders and history, opened by several people alongside their own. Nobody signs into it. In the ordinary case it needs no licence, which is why it is the right answer for most team addresses — accounts@, support@, bookings@.

“In the ordinary case” is doing some work there, and this is where the surprise arrives. An unlicensed shared mailbox is capped at a set size. Cross the cap and it stops accepting mail until you assign a licence. Meeting rooms get the same treatment through room mailboxes, which are also free, and which businesses often buy licences for without realising.

You also need a licence if you want an online archive on the mailbox, or need to place it on legal hold for a dispute or a regulator. Microsoft has changed both the cap and the archive rules more than once, so check the current figures in Microsoft’s own documentation rather than trusting a number in an article. The shape of the problem does not change: the accounts@ mailbox that has absorbed nine years of supplier PDFs is the one that will cost you, and it announces itself by bouncing mail on a Friday afternoon.

Two smaller points. Everyone who opens the shared mailbox needs their own licence — the mailbox is free, the people are not. And when a member of staff leaves, converting their mailbox to a shared one removes the licence cost while keeping the correspondence searchable.

When you genuinely do need to pay

Four tests. If any one is a yes, buy the licence and stop looking for a way round it.

Does it need to sign in? Shared mailboxes have sign-in blocked by design. If something has to log in with that address — a line-of-business application, a scanner, a booking system, an accounts package — you need a licensed account, or another authentication method arranged with the vendor.

Does it need its own files or Teams presence? A shared mailbox has no OneDrive, cannot be a Teams member and cannot hold its own SharePoint content. If reception@ needs to appear in Teams or store its own documents, that is a licensed user.

Will it outgrow the cap? Any address that receives large attachments all day — design proofs, scans, invoices with images — will get there. Budget for it rather than being surprised.

Is it actually a person? A part-time bookkeeper is a person. A contractor who reads company mail is a person. Giving them a shared mailbox and a shared password to dodge a licence saves a few pounds and costs you every audit trail you have.

Everything else — the address on your cards, the one on the contact form, the inbox three people watch — is free.

”We’ll just forward it” is the expensive shortcut

The tempting fourth option is to create nothing at all and set a forward. Mail to sales@ goes to Jane, no mailbox, no licence, done.

It works for about a fortnight, and then it starts costing you in ways that never appear on an invoice.

Forwarding breaks the authentication chain that keeps your mail out of other people’s spam folders. When your tenant forwards a message onward, it becomes the sender to the next hop while the original sender’s domain is still in the headers. Some of that is patched up automatically, but the more you forward, the more often checks fail downstream and the far end bins mail it cannot verify. If you have spent effort on SPF, DKIM and DMARC, forwarding is what undoes it.

It is also a security problem. Automatic forwarding to external addresses is one of the first things an attacker sets up after taking over a mailbox, which is why Microsoft blocks it by default. Every legitimate forward is a rule an investigator has to eliminate later, and a reason somebody turned that protection off.

And it loses the thread. Forwarded mail lands in a personal inbox with no shared history, replies go out under a personal name, and when Jane is on leave nobody can see what came in.

Forwarding earns its place in one situation: a short, dated redirect during a migration or handover, with a note in the diary to remove it.

The short version

Mail just needs to arrive somewhere? Alias. Several people need to see it, reply as it and look back at it? Shared mailbox. Does it sign in, own files, or turn out to be a human being? Licensed user — it was never really a cost question. Forwarding? Only briefly, and write down when you will turn it off.

If your tenant has grown by accretion, this is worth ten minutes with the licence list open. Unused accounts, leavers still licensed, and addresses that should have been aliases are what a licence audit turns up most often. Tidying the addresses is usually small work, and worth settling while anyone is looking at your business email setup.