The fastest way to narrow down an email problem is to work out which part is broken: messages that won't leave your outbox, messages that never arrive, or both. This guide covers email accounts used in apps such as Outlook, Apple Mail, or a phone's mail app. Gmail has a few Google-specific checks of its own, such as shared storage and filters, that are worth looking at if that's your provider.
Start with a webmail test
Sign in to your account on the provider's website and send yourself a short message. The result tells you where to look.
- Webmail works but the app doesn't: the problem is the app, its saved password, or its server settings. Go to the sign-in and server sections below.
- Webmail fails too: the problem is the account or the provider. Check storage, account alerts, and the provider's status page.
- Nothing loads at all: check your internet connection, then try another network such as a phone hotspot.
To check the connection, open a few unrelated websites. If none load, restart your router or switch to mobile data and test again. If websites work but email still fails, continue with the account and app checks below.
If the problem affects Gmail specifically, see our step-by-step Gmail troubleshooting guide.
Quick checks
- Check the recipient's address for typos, and read any error or bounce message. It usually names the cause.
- Look in the Spam or Junk folder for missing incoming mail.
- If a message is stuck in the Outbox, remove large attachments and share a cloud link instead. The attachment may exceed the provider's size limit.
- Set your device's date, time, and time zone to automatic. A wrong clock can break secure connections.
- Check whether your mailbox is full. A full mailbox can block incoming mail.
Fix sign-in and password problems
If the app keeps asking for a password or reports an authentication error, the saved credentials may be out of date, or the provider may require a different sign-in method.
- Sign in on the provider's website to confirm your password works and the account isn't locked or waiting for verification.
- Delete the old password in the mail app and enter the current one.
- Check the provider's help page for third-party app sign-in. Some providers require modern sign-in (OAuth) built into the app, and others need a separate app password when two-step verification is on. Microsoft's help for Outlook.com, for example, says apps connecting over POP or IMAP need modern authentication.
Don't turn off two-step verification just to get an app to connect.
Check the server settings (IMAP, POP, SMTP)
If you set the account up manually, wrong server details will stop sending or receiving. Use the exact settings from your provider's help page, not from a forum post. As an example, Microsoft's current settings for Outlook.com accounts are:
- IMAP or POP server:
outlook.office365.com - SMTP server:
smtp-mail.outlook.com, port 587, STARTTLS encryption - POP and IMAP access are off by default. Turn them on in Outlook.com under Settings > Mail > Forwarding and IMAP.
Work or school Microsoft 365 accounts can use different settings, and an administrator may control them. Many providers use port 993 for IMAP over SSL/TLS and port 587 or 465 for SMTP, but confirm the values for your own provider.
Rule out a network block
Some networks block mail ports, and a VPN, firewall, or security program can interfere. Instead of switching protection off, test the same account on another network, such as a mobile hotspot. If it works there, the first network or router is blocking the connection, and your internet provider or network administrator can help.
Remove and re-add the account, carefully
If nothing else works, re-adding the account clears corrupted settings. First check how it's set up. With IMAP, your mail stays on the server and downloads again. With POP, mail may exist only on that device, so back it up or export it before you remove the account.
What common error codes mean
- 535: authentication failed. Usually a wrong password, an expired app password, or an unsupported sign-in method.
- 550: message rejected or mailbox unavailable. The address may not exist, or the receiving server refused the message.
- 552: size or storage limit exceeded. The message may be too large or the recipient's mailbox full.
- 554: transaction failed. Often a refusal for suspected spam or a policy block.
Wording differs between providers, so the provider's own explanation of the error is more reliable than the number alone.
When to contact support
- Webmail also fails and the provider's status page shows no outage.
- The account says it is suspended, locked, or needs verification and you can't clear it yourself.
- You get the same error after confirming the settings and trying a second network.
- It's a work or school account. Your IT department may need to change a policy or reset the password.
Send support the exact error text and a short list of what you've already tried. That usually saves a round of questions.
What to do next
Begin with the webmail test, since it separates account problems from app problems in about a minute. Then work through sign-in, server settings, and the network, in that order. Re-add the account only when you know your mail is safely stored on the server or backed up.