There is a fair amount of advice online about entering incoming and outgoing server settings, ports and encryption options by hand. For a standard mailbox that comes with your web hosting, that is exactly right, and we have a guide to doing it on an iPhone or iPad.
For Microsoft 365, it is the wrong approach, and it is worth understanding why before you start tapping settings in.
Why the manual route causes trouble
A Microsoft 365 mailbox is not really an IMAP mailbox with a Microsoft badge on it. It is an Exchange mailbox, and Exchange does a good deal more than shuttle messages back and forth.
Set it up properly and your calendar, contacts and shared mailboxes come across with the mail. Everything stays in step: read a message on your phone, and it is read on your laptop before you have put the phone down. Free/busy times work when someone tries to book a meeting with you.
Set it up manually as plain IMAP and you get the mail and nothing else. No calendar, no contacts, no shared mailboxes.
There is a more pressing problem, though. Basic username-and-password sign-in of the sort manual IMAP relies on is exactly what Microsoft has spent years switching off, because it sidesteps multi-factor authentication. So a manual setup either refuses to connect at all, or nags endlessly for a password that never sticks. Almost every “Outlook keeps asking for my password” enquiry we see traces back to an account added the manual way.
Set up multi-factor authentication first. Microsoft now requires it, and getting it in place before you add the account to your devices saves doing the job twice. Our guide to setting up MFA on Microsoft 365 walks through it.
What you actually need
Far less than the manual route. Just your full email address and its password, plus your phone to hand for the multi-factor prompt.
No server names, no port numbers, no encryption settings. Microsoft publishes those for your domain, and your device looks them up. If somebody has sent you a list of server settings for a Microsoft 365 mailbox, you can safely ignore it.
On an iPhone or iPad
You have two sensible options, and which is better depends on how you work.
The built-in Mail app suits most people. In Settings, find Mail, then Mail Accounts, then Add Account, and choose Microsoft Exchange from the list. Apple shuffles this path around between iOS releases, so search Settings for “accounts” if it is not quite where you expect. Enter your email address, tap Sign In when offered, and let it look the settings up. You will be sent to Microsoft’s own sign-in page for your password and your multi-factor prompt, then asked which of mail, contacts and calendars you would like to sync.
The Outlook app is worth it if you live in your inbox, or if you juggle shared mailboxes. It handles those more gracefully than Apple Mail does, and its search is better. Install it, enter your email address, and it does the rest.
Either way you are signing in to Microsoft rather than typing settings, which is the whole point.
On a Windows PC or a Mac
Open Outlook and add the account with just your email address and password. Outlook finds the settings itself, sends you to Microsoft to sign in, and pulls down mail, calendar and contacts.
If Outlook was already set up on that machine years ago with manual settings, and it has started asking repeatedly for a password, the fix is usually to remove the old account and add it again this way rather than to keep re-entering the password.
Shared mailboxes
If your team has a shared address such as accounts@ or info@, do not add it as a separate account with its own password. Give the relevant people permission to it in Microsoft 365 instead, and it appears in their Outlook automatically alongside their own mail.
That way nobody is sharing a password, access can be granted and withdrawn as people join and leave, and replies still go out from the shared address.
If it will not behave
Most Microsoft 365 problems come down to one of three things: an account added the manual way years ago, multi-factor authentication not yet set up, or permissions on a shared mailbox that were never quite right.
All three are quick to sort once you know which one you are looking at. Microsoft 365 is part of what we look after for clients, so if your email is being awkward, ask us and we will take a look rather than leave you working through settings screens.