How to Fix “Server Does Not Support the Connection Encryption Type” in Outlook

Few Outlook errors are as confusing as this one. You click Send, or Outlook tries to connect on startup, and a message appears saying the server does not support the connection encryption type you have specified. Nothing about your password or address has changed, yet your mail suddenly stops working.

This error almost always means one thing: the encryption method selected in Outlook does not match what the mail server expects on that port. The fix is methodical, not difficult. Work through the steps below in order and your account should connect again.

Quick Answer

This error means Outlook is trying to use an encryption method the server does not accept for that port. Open File, Account Settings, then Server Settings, and match the pairs exactly: incoming IMAP port 993 with SSL/TLS, or outgoing SMTP port 587 with STARTTLS (or port 465 with SSL/TLS). Save, restart Outlook, and test. If the pairs are already correct, remove and re-add the account or update Outlook.

Why This Error Appears

When Outlook connects to a mail server, the two sides perform a short negotiation called a handshake. Outlook says, in effect, “I want to talk securely in this way.” If the server is not set up to talk that way on that port, it refuses and Outlook shows this error.

Common triggers include:

• A mismatched port and encryption pair, such as port 587 set to SSL/TLS instead of STARTTLS.
• A provider changing its servers. Providers retire old settings, and an account that worked for years can break overnight.
• Settings copied from an old guide or from a different provider.
• An outdated version of Outlook that does not support the newer TLS versions the server now requires.
• Security software or a firewall interfering with the encrypted connection.

Microsoft documents the standard combinations in its POP, IMAP and SMTP settings for Outlook.com, and nearly every provider publishes an equivalent table. Your settings must match that table exactly.

Step 1: Check Your Incoming Server Settings

1. In Outlook, click File, then Account Settings, then Account Settings again.
2. Select your email account and click Repair, or open Server Settings if that option is shown.
3. Under Incoming mail, note the server name, port, and encryption method.
4. For IMAP, set the port to 993 and the encryption method to SSL/TLS.
5. If your account is POP3 instead, set the port to 995 and the encryption method to SSL/TLS, and tick the option that says this server requires an encrypted connection.
6. Click Next or Done and let Outlook test the settings.

If the incoming side passes the test but sending still fails, the problem is on the outgoing side, which is the more common cause of this exact message.

Step 2: Fix the Outgoing (SMTP) Settings

1. Return to the same Server Settings screen and open the Outgoing mail section.
2. Try the standard combination first: port 587 with encryption set to STARTTLS.
3. Tick “My outgoing (SMTP) server requires authentication” and choose “Use same settings as my incoming mail server.”
4. Save and test by sending a short message to yourself.
5. If 587 with STARTTLS fails, try the second valid combination: port 465 with encryption set to SSL/TLS.
6. Test again after each single change. Do not change the server name at the same time.

The key point is that 587 pairs with STARTTLS and 465 pairs with SSL/TLS. Swapping them is the single most frequent cause of this error. If you want the background on why these pairings exist, our explainer on IMAP and SMTP port choices covers each option in plain language.

Step 3: Confirm the Server Names Are Correct

An encryption error can also hide a wrong server name. If Outlook is pointing at a server your provider has retired, the handshake fails in the same way. Compare both server names character by character with your provider’s current help pages. Watch for small mistakes: an extra letter, a missing dot, or an old domain left over from a previous provider. Business accounts that moved to Microsoft 365 or Google Workspace often still contain the old hosting company’s server names, and those must be replaced, not just re-encrypted.

Step 4: Update Outlook and Check Your TLS Support

Modern mail servers require TLS 1.2 or newer. Very old versions of Outlook, and Outlook running on old versions of Windows, may only offer older protocols the server no longer accepts — and the resulting error can look identical to a wrong-settings problem.

1. In Outlook, go to File, Office Account, Update Options, and choose Update Now.
2. Install any pending Windows updates as well, because Windows provides much of the encryption support Outlook relies on.
3. Restart the computer after updating, then test the account again.

Step 5: Rule Out Antivirus and Firewall Interference

Some security programs scan email by inserting themselves into the connection, and that can break the encryption negotiation. To test this, briefly turn off only the email-scanning feature of your antivirus — not the whole product — and try sending again. If mail works, re-enable scanning and look for an updated version of the security program, or leave the email-scanning component off while keeping real-time file protection on. Also check that your firewall is not blocking Outlook on ports 993, 465, or 587.

Step 6: Remove and Re-Add the Account

If the settings look correct but the error persists, the account profile itself may be corrupted. Removing and re-adding the account rebuilds it cleanly. With IMAP and Microsoft 365 accounts, your mail lives on the server, so re-adding is safe. Before removing a POP3 account, back up your local mail file, because POP3 messages may exist only on that computer. When you re-add the account, let Outlook’s automatic setup run first — it usually selects the correct modern encryption settings on its own.

Common Mistakes to Avoid

• Setting encryption to None just to make the error go away. Even if the server accepts it, your password then travels unprotected.
• Changing several settings at once. You will not know which change fixed it, and you may create a second problem.
• Using a server name from a random forum post. Always take settings from your own provider’s official pages.
• Confusing the incoming and outgoing sections. A correct port typed into the wrong section still fails.
• Re-entering the password repeatedly. This error is about encryption, not credentials; repeated attempts can lock some accounts.

Conclusion

The “server does not support the connection encryption type” error is Outlook’s way of saying the encryption conversation failed before it started. In most cases the repair takes a few minutes: set IMAP to 993 with SSL/TLS, set SMTP to 587 with STARTTLS (or 465 with SSL/TLS), confirm the server names against your provider’s table, and keep Outlook updated. Change one thing at a time, test after each change, and your mail will be flowing again with its encryption intact.

Frequently Asked Questions

Does this error mean my account has been hacked?

Almost certainly not. It is a settings mismatch between Outlook and the server, not a security breach. Your mail is not being read; Outlook simply cannot agree with the server on how to encrypt the connection.

Which encryption should I pick: SSL/TLS or STARTTLS?

It depends on the port. Use SSL/TLS with ports 993, 995, and 465. Use STARTTLS with port 587 (and with port 143 for IMAP if a provider requires it). The port decides the answer.

The error only happens when sending, not receiving. Why?

Incoming and outgoing servers are configured separately. Your incoming pair is probably correct, while the outgoing port and encryption do not match. Focus on the SMTP section: try 587 with STARTTLS, then 465 with SSL/TLS.

Why did this start suddenly when I changed nothing?

Providers regularly retire old ports and older TLS versions for security reasons. When they do, accounts using the old combination stop working without any change on your side. Updating your settings to the current published values fixes it.

I use Outlook for a work account. Should I change settings myself?

If your employer manages your mailbox, check with your IT team first, because they may push settings automatically. If it is your own business account with a hosting provider, use that provider’s published settings table.