Email won't send on your broadband? Fixes to try

Your email app talks to two separate servers:

• The incoming server uses IMAP or POP3. IMAP keeps your mail on the server and syncs it across devices; POP3 downloads it to one device.
• The outgoing server uses SMTP (Simple Mail Transfer Protocol), the system that hands your message on towards the recipient.

Each has its own server name, port (a numbered doorway on the server), encryption setting and sign-in. If the outgoing details are wrong, or the app doesn't sign in to the SMTP server, mail keeps arriving while everything you write sits in the Outbox.

BT requires SMTP authentication on all sent email to keep spammers off its server, and Virgin Media says that without SSL and SMTP authentication you'll get error messages when sending or receiving.

If web pages won't load either, it isn't an email problem; see our guide to Wi-Fi that's connected but has no internet.

1. Send yourself a test from webmail

BT's first step is to log in to webmail and send yourself a test email; if that works, check your email program's settings. TalkTalk says that if webmail works but your app doesn't, it's possible the app's settings are the issue. If webmail won't send either, the problem is with the account: see the error messages below.

2. Think about recent password changes

Sky and Virgin Media both say a password change has to be carried into your email apps. If your app keeps asking for your Sky password, Sky says the password hasn't updated properly, for example after a reset in a browser; sign in to Sky Yahoo Mail on the web (completing a CAPTCHA, a letters-and-numbers check, if shown) or use Sky's "Unlock your emails" link, and if mail still fails, remove the account from the app and add it again.

3. Look in the Outbox

BT says that if it detects a large number of emails sent in a short time you'll see error 421; wait at least an hour and delete stuck emails in the Outbox. BT says the limit is lower for seven days after an account recovery.

4. Check your mailbox isn't full

TalkTalk says that when a mailbox reaches its quota (10GB or 700,000 emails, checked October 2026) you can't send or receive.

5. Look at who you're sending to, and how

TalkTalk says a "too many recipients" message means trying again with a smaller group; Sky says it can temporarily suspend sending after suspicious activity such as repeated attempts to send one message to over 100 recipients. If you're connected through a VPN (a service that routes your traffic through another server), BT's advice for its 553 spam-filter error includes making sure you aren't using one; see our guide to using a VPN on home broadband.

These are the outgoing (SMTP) settings each service publishes for email apps. The settings belong to the service that gives you your email address: a Gmail address uses Google's published settings and a BT address uses BT's.

Sources: each service's own help pages. Virgin Media says that once a mailbox has moved to Junara you shouldn't need to change any email settings, and Junara says the same; if an app fails after the move, check Junara's own support pages.

Several services now limit apps that simply store your main password, so an older setup can stop sending.

BT Email

BT's sign-in is straightforward: your full address and BT email password, with SMTP authentication switched on. BT says errors 530, 550 and 0x800ccc79 when sending all mean the app isn't signing in properly, and the fix is to turn on SMTP authentication.

Virgin Media Mail

Virgin Media says email apps need a separate app password (a password made just for email apps in the My Virgin Media app), not your My Virgin Media sign-in password, because IMAP and POP don't support extra protection such as multi-factor authentication.

Virgin Media is also moving all its email (@virginmedia.com, @blueyonder.co.uk, @virgin.net and @ntlworld.com) to Junara, a paid service billed per address. If you didn't sign up by the date in Virgin's emails, your mailbox is suspended and email apps such as Outlook or Apple Mail show an error when you send or receive; Virgin says you then have an extra 120 days to sign up before the mailbox is deleted. Its emails contain no sign-up link, so treat any "pay now to keep your email" link as a red flag and sign up only through Virgin Media's help page or Junara's website.

Sky Yahoo Mail

Sky says it no longer lets you create app passwords. New app setups use your Sky iD password; if you set an app up with a 16-digit app password in the past, Sky says it keeps working even after you change your Sky iD password. Sky lists Outlook 2010 to 2019, Outlook 365 on Windows, Windows Live Mail and older Apple Mail (iOS 8 or macOS 10.10 and earlier) as out of date for Sky email, and recommends current Apple Mail, Gmail on Android, and Outlook for iOS and Android. You can always use Sky email at sky.com.

Windows Mail users

If you use the Mail app built into Windows, the cause may not be your settings at all. Microsoft ended support for the Windows Mail, Calendar and People apps on 31 December 2024 and says they can no longer send or receive email. Sky's help pages still list Windows 10 Mail as recommended, but Microsoft's end of support is what counts. Microsoft recommends moving to the new Outlook for Windows or Outlook.com; webmail works in the meantime.

Outlook.com and Hotmail

Microsoft says Outlook.com requires the use of Modern Auth, also called OAuth2, so your email app has to support that sign-in method. Microsoft adds that some devices may need an app password if your account password isn't recognised.

Gmail

Google says Gmail no longer supports third-party apps or devices that need you to share your Google username and password. Look for "Sign in with Google" in the app. Google's 16-digit app passwords only work with 2-Step Verification on, and Google says they aren't recommended and are unnecessary in most cases.

Sometimes the block is in your broadband connection, not your email account. Port 25 is the traditional SMTP port, and some providers block it to cut spam sent from hijacked computers.

For example, ISPreview, the UK broadband news site, reported that YouFibre would block port 25 from 16 January 2026 because spammers commonly exploit it, often from compromised computers on its network. Webmail users were said to be unaffected; people sending from email apps on port 25 were told to switch to port 587 or 465 with SSL/TLS. ISPreview noted that various other providers have blocked port 25 over the years. We haven't found a published statement from BT, Sky, TalkTalk or Virgin Media saying whether their broadband blocks it, so we won't guess.

The fix is the same either way: every service in the table above publishes port 465 or 587 for email apps, so move any app still sending on port 25 to its service's published port.

If your provider has written to say a device at home is sending spam or has malware, don't just change ports and carry on. Our guide on what to do when your provider says a device is infected explains how to find and clean the device.

These are the meanings the providers give (checked October 2026). The same number can mean different things with different services: BT's 553 is its spam filter, while Sky links Outlook's 553 to an unverified address.

Your email account belongs to whoever provides the email, not to the line. Moving your broadband doesn't move your email, but leaving a provider can change what its email account lets you do.

Your old provider's email account may have changed

• BT: BT says its free Basic email for people leaving BT Broadband has to be ordered when you cancel, works only at bt.com rather than in an email app, and needs you to log in regularly to stay active. So if you chose Basic, an app that stops sending is expected: use webmail, or BT's paid Premium Email for the full service.
• TalkTalk: TalkTalk says that without active broadband and without its paid Mail Plus service you lose the ability to use the address. If Mail Plus payments are missed, the account is reduced to a basic service and eventually deleted.
• Virgin Media: the move to paid Junara email (above) applies to every Virgin Media address, whether or not you still have Virgin broadband, so leaving isn't what decides it: your sign-up date is.
• Sky: We couldn't find a Sky page saying whether you keep Sky Yahoo Mail after leaving, so ask Sky. Sky does say accounts unused for six months may be deleted, and auto-forwarding without signing in can make one look inactive.

Our guide to keeping your email address when you switch broadband sets out each provider's options and costs in full.

Your new connection may treat port 25 differently

If your app still used port 25 and your new provider blocks it, sending fails although your email account hasn't changed: move the app to its published port.

If TalkTalk is your email provider

TalkTalk went into administration and BT bought its consumer and wholesale (PXC) businesses out of administration on 5 October 2026. The Competition and Markets Authority is reviewing the deal under a public-interest intervention notice and is due to report by 19 October 2026; until then BT and TalkTalk are run separately and nothing changes for TalkTalk customers. TalkTalk's published email settings (checked 14 October 2026) are the ones in the table above, so keep using them.

Contact your email provider if webmail won't send either, if sending has been suspended or limited, or if the same error keeps appearing after you've checked every setting. If webmail works and the settings match, TalkTalk says it's best to contact the app's provider.

Before you get in touch, write down:

• the exact error code or message, and when it first appeared;
• which app and device you use, and whether the app is up to date;
• whether webmail can send;
• your outgoing settings (server, port, encryption, authentication), or a screenshot;
• anything that changed recently, such as a new password or a switch of broadband provider.

If it could be a hacked account

If sending is blocked and you also see things you didn't do, such as unfamiliar messages in Sent or a password that suddenly doesn't work, follow our guide on what to do if your provider email account is hacked. Be wary of anyone contacting you out of the blue offering to fix your email; our guide to broadband scam calls and emails explains the warning signs.