Outlook reports errors with codes that mean nothing to anyone. The good news: nearly all of them come down to three things — the username is not the full address, the port or security type is wrong, or outgoing mail is not authenticated.
First, the 10-second test
Open webmail . If it works there, the server is fine and the problem is Outlook — read on. If it fails there too, the problem is ours .
The errors that come up most
| Code or symptom | Most likely cause |
| 0x800CCC0E | Cannot reach the server: server name mistyped, wrong port, or the network blocking it. Corporate networks and some mobile operators block mail ports. |
| 0x80042109 | Cannot connect to the outgoing (SMTP) server — it never even gets to the password. Almost always the port 465 blocked by the network: many carriers and corporate networks close it. Switch the outgoing server to port 587 with STARTTLS and try again. |
| 0x800CCC92 or 0x800CCC90 | Authentication failed. The username must be the full address, not just the name. |
| Keeps asking for the password | Outlook stored an old password. Delete the entry in Windows Credential Manager and enter it again. |
| Cannot send (receiving is fine) | The option "My outgoing server requires authentication" is off. This is the number one cause of this symptom. |
| Certificate warning | You are using a server name that does not match the certificate. Use mail.yourdomain, not the machine name. |
| Duplicate messages, or messages vanishing from the phone | The account is set to POP instead of IMAP. POP downloads and removes from the server; with more than one device, always use IMAP. |
The correct settings
| Field | Value |
| Username | The full address (name@yourdomain). |
| Incoming server (IMAP) | mail.yourdomain — port 993, security SSL/TLS. |
| Outgoing server (SMTP) | mail.yourdomain — port 465, security SSL/TLS. |
| Outgoing server — alternative | mail.yourdomain — port 587, security STARTTLS. Use this one if 465 does not work: it does exactly the same job and gets through networks that block 465. |
| Outgoing authentication | On, using the same credentials as incoming. |
The step-by-step with screenshots is in how to set up e-mail in Outlook .
| Careful about removing the account to "start fresh". If the account is POP, the messages exist only on that computer — removing it can delete them. Take a copy first. |
| If it broke suddenly and used to work ask what changed: new password, new computer, or a different network. Switching from Wi-Fi to mobile data (or the reverse) fixes it instantly when the network is to blame. |
|
Send us the error code and a screenshot — we will pin it down. Open a support ticket |
|
SEE ALSO If Outlook is not erroring but hiding messages, the junk filter is the issue: How to stop spam in Outlook: the filter on your computer and the one on the server. |
|
PROFESSIONAL E-MAIL Your e-mail should carry your company name. Mailboxes on your own domain, with webmail, antispam and automatic setup on phone and desktop. See e-mail plansWorks in Outlook, on your phone and in the browser |
- 0 Users Found This Useful
