Sometimes you’ll open your email client and your email will arrive in your inbox, but when it comes to sending a message you get an error message. Here are the steps to follow for Outlook, Thunderbird etc to fix this. All the settings mentioned are for GreenNet users. (If you’ve come here from a web search and use an email service other than GreenNet, the server names will be different depending on your email provider, and maybe some of the port numbers too.)

This is particularly likely to occur when travelling and connecting through a different ISP from normal, because the ISP may block outgoing ports as a safeguard against their connections being used to send spam.

Instructions for changing the port (and sometimes which port to use) may vary depending on the exact version of the email program you are using, but the following covers most of the common ones. Other causes for not being able to send include an invalid recipient address: it’s usually worth recording any error message you see on screen, however cryptic.


The usual symptom is that Thunderbird will try to send for about 20 seconds before giving up with “Sending of message failed. The message could not be sent because the connection to SMTP server timed out.”

  1. Click on Account Settings (usually on the Tools menu)
  2. Right down the bottom of the list of accounts on the left, should be “Outgoing server (SMTP)”. Click that.
  3. On the top right of the Account settings dialogue box you should see one or more outgoing servers. You probably want the default, which might mention ‘’. Click that and ‘Edit’.
  4. Server name should be If the server name does not end or, then possibly you aren’t sending out through GreenNet, and can either check with the service you are using, or switch to GreenNet. Make sure “Use name and password” is ticked; the username is usually the bit before the @ sign in your email address, or the username you use to log into GreenNet Webmail. The first time you send, Thunderbird may ask you for your GreenNet password.
  5. If the port number listed is “25”, try altering it to “2525” and you can try “none” for “connection security” while you try to get it working (security is optional on 2525). Click “OK” and try sending again.
  6. If that doesn’t work, you might also want to try port 587, which requires STARTTLS security. In fact this is the preferred option for security reasons.

If you’re still having problems, please let us know, telling us any error message and the software you are using.

Outlook Express and Windows Mail

  1. Go to Account Settings (Tools > Accounts)
  2. Click on the “Mail” tab
  3. Highlight your GreenNet email account, and then click on “Properties”
  4. On the “Servers” tab, check that you are using GreenNet’s SMTP server. Outgoing mail (SMTP) should read “”
  5. Make sure there is a tick in “My server requires authentication” (the “Settings” should be “same settings as incoming”).
  6. Next, click on the Advanced tab, under ‘Server Port Numbers’ change the Outgoing mail server port from 25 to 2525 (or vice versa, depending on which one you have there already. You could also try 465 with encryption).
  7. Save your changes and try sending email again.

Outlook 2007, 2010 and 2013 (and Outlook 2003 SP2 and above)

  1. Go to Tools menu > Account settings
  2. Select the relevant GreenNet email account, and click the “Change” button (third from the left above that line)
  3. Make sure that the “Outgoing mail server (SMTP)” box reads “” if this is a GreenNet account. (If you have “” it is worth changing to “”.)
  4. Click the “More settings…” button to the bottom right.
  5. Click the second tab along, “Outgoing server” and ensure “My outgoing server (SMTP) requires authentication” is ticked. Select “Use same settings as my incoming mail server”. “Require secure password authentication” should not be ticked.
  6. Click the right-hand tab, “Advanced”.
  7. For “Outgoing server (SMTP)”, remove “25” if that is what you have, and first try entering 587. In this case change “Use the following type of encrypted connection” to TLS. Click “OK” and next.
  8. Cancel any messages being sent, and try sending again.
  9. If you still get an error, you may want to try using “2525” “Outgoing server (SMTP)” without any encryption (not secure), or possibly “465” with SSL encryption (secure).

Another reason Outlook may not be sending is because there’s a large message stuck in the outbox and Outlook keeps resending. First try File > Offline and deleting the message, or if that doesn’t work, use the Windows Start > Search for “outbox”, wait, right-click the message and choose delete (thanks to Diane Poremsky . Doesn’t work on Windows 8.)

Outlook 2003

Older releases of Outlook 2003 use port 465 for a secure connection, and won’t do port 587. So first we’ll try 465, and if something objects to that, fall back on port 2525.

  1. Go to Tools > Email Accounts
  2. Select “View or change existing e-mail accounts” and click “Next”
  3. Select the relevant GreenNet email address and click the “Change…” button
  4. Make sure that the “Outgoing mail server (SMTP)” box reads “” if this is a GreenNet account. (If you have “” it is worth changing to “”.)
  5. Click the “More settings…” button to the bottom right.
  6. Click the second tab along, “Outgoing server” and ensure “My outgoing server (SMTP) requires authentication” is ticked. Select “Use same settings as my incoming mail server”. “Require secure password authentication” should not be ticked.
  7. Click the right-hand tab, “Advanced”.
  8. For “Outgoing server (SMTP)”, remove “25” if that is what you have, and first try entering 465. If you have a tick box with “This server requires a secure connection (SSL)”, tick it. (If you instead have a question about “encrypted” connection with a choice of “TLS”, choose that and port “587” as above.)
  9. Click “OK” and next and “Finish”.
  10. Cancel any messages being sent, and try sending again.
  11. If you still get an error, you may want to try using “2525” “Outgoing server (SMTP)” without encryption (not secure).


Windows Live Mail 2009 and above

This is the email program that comes with “Microsoft Live Essentials” for Windows 7 and 8 (not the same as the “Windows 8 Mail” program). (Technical note: Microsoft now prefers STARTTLS like the rest of the world, but only on ports 587 and 25.)

  1. Right-click on your GreenNet email account and choose “Properties…”
  2. Click on the second tab along, “Servers”
  3. Ensure “my server requires authentication” is ticked. (If you click “More settings…” it should show “Use same settings as my incoming mail server”)
  4. Click the “Advanced” tab to the top right.
  5. In the top box “Outgoing server (SMTP)” try 587 and tick “This server requires a secure connection (SSL)”.
  6. Click “OK” and “Close”.
  7. Try sending mail again. If you have problems, try port 465 (with SSL), or as a last resort 2525 (with SSL unticked).


Windows 8 Mail

It is suggested you upgrade to a better email program, such as Thunderbird. If you have no other option:

  1. Start Windows 8 mail
  2. Wave your mouse over the bottom right of the screen to get the “charm menu”
  3. Choose “settings”, then “accounts”
  4. Select the GreenNet account
  5. Scroll down to the “Outgoing (SMTP) email server” and
  6. On earlier versions port 587 may not work correctly, so use port 465 and tick “Outgoing server requires SSL
  7. Tick the “requires authentication” and “use same settings” below that boxes as well and click “Connect”.


Apple Mail (Mac OS X)

Later versions of Mac Mail may be able to automatically choose automatically between 465, 587 or 25, which should work in most cases.  As well as problems with ports, note that Mail stores outgoing credentials (username and password) separately from incoming credentials, and so if the outgoing password has not been updated, that may explain why you cannot send.

  1. Go to Mail menu > Preferences
  2. Click the Accounts icon “@” along the top
  3. Select the GreenNet account
  4. If you have OS X 10.9 or later, select the “Advanced” tab. If the top setting is “Automatically detect and maintain account settings” and that is ticked, untick it and then close the Preferences box. Click “Yes” in answer to saving the settings (it may prompt for the password), and then reopen the Preferences box.
  5. Select the “Account information” tab
  6. At the bottom should be “Outgoing Mail Server (SMTP)”. To the right of that click the list, and choose “Edit SMTP server list”.
  7. Older version of Apple Mail: If there is no list, there may be a button marked “Outgoing server” to click and the port setting is more likely to be relevant. See “Note for old versions” below. Otherwise continue immediately below.
  8. Newer version: click the Account Information and ensure the server name is Click “Advanced”, and tick “Use SSL”. Also click “Authentication” and change to “Password”. Your user name is usually the part before the “@” sign, and is not the full address.
    1. If you’ve changed these, they are more likely to be the problem than the port, so make sure you are using the default ports (25, 465 and 587), Click “OK” and save and try again.
    2. If this still doesn’t work, go back to the Account Information > SMTP list > Advanced and try port 587 and try again. If this fails, try changing from default ports, use port 2525, and turn off “Use SSL” (not encrypted).

Note for old versions: you should have a box marked “SMTP Server Options”. Ensure “Outgoing mail server” is “”, change server port to 587, tick “Use Secure Sockets Layer (SSL)”, Authentication=password, and user name and password as above.

Intermittent failure to authenticate on Mac Mail under OS X Yosemite

Intermittent failures to send, usually producing messages like “SMTP connection to server failed” have been reported many times from October 2014 onwards. The bug appears to affect different accounts at different times and is still reported as of February 2015.

Try the procedure in the previous section first, checking that SMTP authentication is set to “Password”, and retype your password. If it has been working sometimes using the same connection (eg wifi, broadband), you probably don’t need to change the port number. Also in these SMTP server advanced settings, and the other server settings, if there is an option “Automatically detect and maintain settings” (seems to be there from OS X 10.10.1), please untick this. If you have changed anything, try sending the message again.

If you are still having the problem, again go to Mail > Preferences > Accounts > Edit SMTP server list > Advanced and ensure “Allow insecure authentication” is ticked (this option, if available, allows plain password authentication although it is still over a SSL/TLS encrypted connection and so secure). Try again. If this stops working again, the following procedure is suggested.

  1. Close Mail
  2. In Finder, choose Go > “Go to folder”, enter ~/Library/Mail/V2/MailData/ or otherwise navigate to the MailData folder
  3. Select the file Accounts.plist and copy it to your desktop as a backup
  4. Back in the MailData folder, double click it to open in TextEdit or use some other text editor
  5. For each account there is a line that says UserAllowsInsecureAuthentication
  6. underneath that line is a – change this to
  7. Close the text editor and save the file
  8. Launch Mail and try again

The above workaround is based on an Apple Forums posting. Other common Yosemite issues are listed here. You may also want to report your problem to Apple.

Outlook 2011 for Mac

  1. Start Outlook
  2. Go to the Tools menu, then select Accounts
  3. You probably just have one account on the left-hand side. If you have
    more than one, select the GreenNet account.
  4. Down the bottom you should have “Outgoing server” which should be Under that, make sure “Override default port” and “Use SSL to connect” are both ticked. The box to the right of the “outgoing server” “:” should read “587”.
  5. Then click “More Options..”
  6. click “Authentication” and select “Use Incoming server info”
  7. Click “OK” and close the Accounts window.

iPhone/iPad etc

As with Apple Mail, likely causes of not being able to send are (a) port blocking; or(b)  changing your password and only updating it under the incoming mail server settings.

  1. Go to Settings
  2. Tap "Mail, Contacts, Calendar", or "Mail" (depending on device version)
  3. Tap "Accounts"
  4. Select your account
  5. Scroll down to the "Outgoing Mail Server" heading, and tap 'SMTP >'
  6. Under "Primary Server", tap ""
  7. Ensure that the settings are set to:
    Host Name:
    Username: (Your GreenNet email username)
    Password: (Your GreenNet email password)
    Use SSL: On
    Authentication: Password
    Server Port: 587
  8. Tap "Done".

More information and alternatives

This problem is usually due to ISPs or the network you are on blocking normal access to port 25 because of spam being sent via their network. Although it’s very inconvenient when it is blocked, the steps above should allow you to get around the issue. An alternative when you are in an institution like a university is to contact their IT support and ask them to lift the block for you. It’s a good idea to use secure connection (TLS) when available as it not only makes it much harder to eavesdrop on your messages, but protects your password when you are using a wireless network.

For the Eudora email program, and for more information about how to diagnose the problem when it may also be anti-virus software, please see Diagnosing problems sending or receiving in Eudora. If you’re still having problems, please let us know, telling us any error message and the software you are using.

For short periods, you might be content to use webmail.