Have you ever tried sending an email and received the error message “SMTP Error 535-5.7.8: Username and Password Not Accepted“? If so, know that you are not alone. This is a common error that occurs when your email client cannot authenticate with the mail server. But don’t worry – like most errors, this is also fixable. Today, you will learn what error 535-5.7.8 means, why it happens, and how to fix it quickly. Even if you are not a tech pro, this article will help you understand and resolve the issue. Let’s begin!
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What is SMTP Error 535-5.7.8: Username and Password Not Accepted?
Stand for Simple Mail Transfer Protocol, SMTP is the technology that allows email to be sent and received over the internet. When you see Error 535-5.7.8: Username and Password Not Accepted – it means that the email server rejected your login credentials. In simple words, your email client is trying to log into the mail server, but the server is denying access because of incorrect authentication details. This can happen due to many reasons, which we will cover next.
Common Causes of SMTP Error 535-5.7.8: Username and Password Not Accepted
There are many reasons why this error may appear. Here are the most common ones:
Incorrect Username or Password
You may have entered the wrong email or password in your email client.
Or, your password may have changed, but the email client is still using the old one.
Two-Factor Authentication (2FA) is Enabled
If you have enabled 2FA on your email account (especially for Gmail, Yahoo, or Outlook), the email client may require an App Password instead of your regular password.
Server Configuration Issues
Your SMTP settings (hostname, port, or encryption type) may be incorrect.
Or, your email provider may have changed authentication methods, requiring an update in your email client settings.
IP Blocking or Suspicious Activity
If the server detects multiple failed login attempts, it may temporarily block your IP for security reasons.
Some email providers block logins from unknown locations for security. Check with your email provider or you can also get support from Lease Packet. Lease Packet is the master provider of emailing services & support.
Outdated or Incorrect Email Client Settings
If you are using an outdated email client, it may not support modern authentication methods.
Some email clients use older security protocols that the email provider may have disabled.
How to Fix SMTP Error 535-5.7.8: Username and Password Not Accepted
Now that you know the possible causes, let’s go through some quick fixes of error 535-5.7.8: Username and Password Not Accepted.
Check Your Username & Password
You must make sure that you have entered the correct email and password. Double check!
If you recently changed your password, update it in your email client.
Generate an App Password (If 2FA is Enabled)
If your email account has two-factor authentication (2FA) enabled, you must use an App Password instead of your regular password.
- To generate an App Password in Gmail:
- Go to Google Account Settings.
- Select Security > App Passwords.
- Generate and copy the App Password.
- Paste it into your email client instead of your regular password.
Update SMTP Settings
Make sure you are using the correct SMTP settings for your email provider. For example:
For Gmail:
- SMTP Server: smtp.gmail.com
- Port: 465 (SSL) or 587 (TLS)
- Authentication: Required
- Username: Your full email address
- Password: Your email account password or App Password
For Outlook:
- SMTP Server: smtp.office365.com
- Port: 587 (TLS)
- Authentication: Required
Check for IP Blocking
If you suspect that your IP is blocked, try logging into your email via a web browser.
If you receive a security warning, follow the instructions to verify your login.
Some email service providers like Lease Packet allow you to whitelist your IP in security settings.
Update or Reinstall Your Email Client
If you are using an older version of Outlook, Thunderbird, or any other email client – update it to the latest version.
If updating doesn’t work, try removing and re-adding your email account in the client.
Advanced Technical Guide to Fixing the Error 535-5.7.8: Username and Password Not Accepted
If the above fixes don’t work, here are some advanced solutions:
Check Server Logs (For Mail Server Admins)
If you own a mail server, check email logs to see if any login issues.
Enable Less Secure Apps (For Testing Only)
Some email providers block older authentication methods.
In Gmail, you can temporarily enable Less Secure Apps via security settings, but this is not recommended for long-term use.
Verify Firewall and Antivirus Settings
Sometimes, firewall or antivirus programs block email client connections.
Try disabling your firewall temporarily to check if it resolves the issue.
Contact Your Email Provider
If nothing works, reach out to your email provider’s support team to check if there are server-side restrictions causing the issue. You can also connect with Lease Packet for support.
How Lease Packet Can Help with Error 535-5.7.8: Username and Password Not Accepted?
At Lease Packet, we provide secure and reliable email solutions for businesses & individuals. If you are facing SMTP authentication errors, we can help you:
- Set up and configure your email server properly.
- Troubleshoot authentication issues with expert support.
- Secure your email communication with advanced security protocols.
If you need a trusted email service provider, Lease Packet is here to assist you. Connect with us for queries!
Bottom Line
SMTP Error 535-5.7.8: Username and Password Not Accepted can be frustrating, but it’s fixable with the right approach. The most common reasons for this error are incorrect login credentials, 2FA settings, outdated SMTP configurations, or IP restrictions. Follow the solutions provided above and see if you can resolve the issue and send emails without any trouble. If you need further assistance, Lease Packet can help you with professional email solutions & support. Connect with Lease Packet experts for quotes & queries!
Why am I seeing SMTP Error 535-5.7.8?
This error occurs due to incorrect login credentials, 2FA settings, or outdated SMTP configurations.
How can I quickly fix this error?
Check your username and password, update SMTP settings, and use an App Password if 2FA is enabled.
Can Lease Packet help with email setup and troubleshooting?
100%! Lease Packet provides expert support to fix email authentication errors and ensure smooth email communication. Contact Lease Packet today!