Outlook can usually set up an account from just the address and password, and when it works there is nothing more to do. When it does not, the cause is almost always that Outlook guessed the server settings instead of asking you, and the fix is to stop it guessing.
Get the real settings first
In cPanel, open Email Accounts, find the mailbox and use Connect Devices. It shows the exact settings for that account instead of the generic ones.
They will look like this:
Incoming (IMAP) mail.yourdomain.com 993 SSL/TLS Outgoing (SMTP) mail.yourdomain.com 465 SSL/TLS or 587 with STARTTLS Username the full address, [email protected]
Two of those are where people go wrong. The username is the whole address: entering just the part before the @ rejects a correct password. And outgoing authentication must be switched on, which Outlook does not always do by itself.
Adding the account manually
Automatic setup works by looking for configuration published under your domain, and when that is absent Outlook guesses at common server names. The guesses are frequently wrong, and the resulting error message says the password is incorrect, which sends people off resetting passwords that were fine.
To configure it properly, choose the manual setup option and select IMAP rather than letting Outlook decide. Enter the incoming and outgoing servers exactly as cPanel gave them.
Then open More Settings and go to the Outgoing Server tab. Tick My outgoing server (SMTP) requires authentication and leave it set to use the same credentials as the incoming server.
That tick is the single most common missing setting in Outlook. Without it, receiving works perfectly and sending fails with a relay error that reads like a server problem.
On the Advanced tab, set the ports and encryption to match cPanel's values. Then test.
IMAP, not POP3
Choose IMAP. Mail stays on the server and syncs with your phone and webmail, so a message read on one device shows as read on the others.
POP3 downloads mail and typically removes it from the server. Choosing it in Outlook is how mail ends up existing only inside one laptop's data file, which becomes a problem the day that laptop does.
If an account is already set up as POP3, changing it means adding the account again as IMAP rather than converting it.
Cached mode and the local data file
Outlook keeps a local copy of the mailbox in an OST file, and syncs it. This is why it works offline and why it sometimes shows something different from webmail.
When Outlook shows stale mail, or a folder that no longer exists, the local copy has drifted. Sending and receiving forces a sync; if that does not resolve it, removing the account and adding it again rebuilds the local file from the server.
Nothing is lost by rebuilding an IMAP account's local file, because the server holds the mail. This is not true of a POP3 account, where the local file may be the only copy. Another reason to use IMAP.
Deciding what stays offline
Outlook defaults to keeping a limited period of mail locally, often a year. Older mail is on the server and visible, but not searchable offline.
If searches are missing old messages that definitely exist, this setting is why. It is adjustable in the account settings, and setting it to keep everything uses more disk in exchange for complete local search.
Common failures
Password rejected but you are certain it is right. The username is not the full address, or automatic setup guessed the wrong server. Configure it manually.
Receiving works, sending fails. SMTP authentication is not ticked. This is the answer nearly every time.
Sending times out. The port is blocked. Many networks block 25; use 465 or 587.
Certificate warning on connection. The server name does not match the certificate. Use the exact hostname cPanel gave you instead of a shortened version.
Mail appears in webmail but not in Outlook. The mailbox is fine and Outlook is not syncing that folder, check the folder is subscribed in the IMAP folder list. Accessing webmail explains using it to isolate exactly this.
Everything worked and suddenly stopped. Check the mailbox is not over quota before investigating Outlook at all: a full mailbox rejects mail regardless of the client.
When it refuses to connect at all, one command from a terminal says whether the settings or the server is at fault. How to Diagnose a Mail Client That Will Not Connect picks it up from there.
Prove the server works before blaming the client
Most reported client faults are settings, and testing the server directly separates the two in a minute.
openssl s_client -connect mail.example.com:993 -servername mail.example.com </dev/null 2>/dev/null | tail -5 openssl s_client -connect mail.example.com:587 -starttls smtp </dev/null 2>/dev/null | grep -i auth
A successful connection with a valid certificate means the server is fine and the problem is on this machine. The authentication line lists what the server accepts, and a client configured for a method not listed fails with a password error even though the password is correct.
Try webmail before anything else as well. If mail arrives there, the mailbox and the server are working and the entire investigation belongs to the client. Accessing webmail covers reaching it.
When automatic setup finds the wrong server
Modern clients try to configure themselves before asking anything, and a stale record sends them to a provider you left years ago.
dig autodiscover.example.com CNAME +short dig _autodiscover._tcp.example.com SRV +short dig autoconfig.example.com A +short
The signature is distinctive and confusing: manual settings work perfectly and automatic setup does not, so new staff have problems and existing staff do not.
Remove records belonging to providers no longer in use. Until they are gone, every new mailbox on the domain will be configured against the wrong server by a client trying to be helpful.
The local file, and why mail disappears
The client keeps its own copy of the mailbox, and that copy is where most alarming reports come from.
Mail that vanished, folders that emptied, or a mailbox that stops updating are usually a local data file that has grown past what it handles well or has become damaged. The server copy is intact throughout, which is easy to confirm and worth confirming first.
Before repairing anything, check the same account through webmail. If the mail is there, nothing has been lost and the fix is local. If it is not there, the problem is the mailbox rather than the client, and repairing the local file would have achieved nothing. Diagnosing a mail client that will not connect deals with the connection half.