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Unable to Send Emails, Receiving is Fine (How to Fix)

If you can receive but are unable to send emails, the issue is usually related to your outgoing mail server (SMTP) configuration. 

This guide will help you: 

  • Identify why sending emails fails 
  • Correct your SMTP settings 
  • Restore normal email delivery 

Most cases of being unable to send emails are caused by simple configuration issues, such as incorrect ports or authentication settings. 

By the end of this guide, you’ll confidently diagnose and resolve sending issues if they are due to the outgoing mail server configuration without unnecessary support escalation. 

Unable to Send Emails
Table of Contents

Why This Happens 

Email uses two different server connections: 

Function Protocol 
Receive email IMAP / POP3 
Send email SMTP 

Because these systems are separate, receiving mail can work normally even when sending fails. 

Common Causes 

Most sending issues occur due to: 

Step-by-Step Fix  

1: Test Sending via Webmail 

Log in to Webmail and attempt to send a message. 

  • If webmail cannot send, the issue may be server-level. 
  • If webmail sends successfully, the problem is your email client configuration. 
2: Confirm the Full Error Message 

Check the message displayed in your email client. 

Common errors include: 

  • Message stuck in the outbox 
  • Sending failed 
  • SMTP authentication required 
  • Cannot connect to the SMTP server 
  • Connection timed out 

If you see a specific SMTP error code, refer to our SMTP Error Codes guide. 

3: Verify Your Outgoing Mail Server (SMTP) Settings 

SMTP 535 Authentication Failed errors usually happen when your email client cannot successfully log in to the outgoing mail server. 

Correcting the settings restores secure authentication and allows your email client to send messages normally. 

This step ensures that your SMTP authentication, port, encryption, and credentials are configured correctly in your email application. 

What This Step Fixes 

Correct SMTP configuration resolves issues such as: 

  • SMTP 535 Authentication Failed 
  • Incorrect login credentials 
  • Email clients are not authenticating with the server 
  • Incorrect SMTP port or encryption settings 
  • Sending restrictions due to authentication failure 

These adjustments restore secure email sending. 

What to Check 

After locating the SMTP configuration screen, confirm: 

  • Outgoing server authentication is enabled 
  • Username is your full email address 
  • Password is correct 
  • Port is 465 (SSL) or 587 (TLS) 
  • Encryption is enabled (SSL/TLS) 

Incorrect authentication or disabled encryption are among the most common causes of SMTP 535 errors. 

Recommended 1-grid SMTP Settings

Before adjusting your email client, confirm that you are using the correct server settings. You can find your settings via your cPanel, or Windows Plesk Control Panel, if you need to double-check that these correspond with your email client configuration.

Outgoing Mail Server (SMTP) 
  • SMTP Server: mail.yourdomain.co.za 
  • Port (SSL): 465 
  • Port (TLS): 587 
  • Encryption: SSL or TLS 
  • Authentication: Enabled 
  • Username: Your full email address (e.g. [email protected]) 
  • Password: Your email account password 

TIP: 
Always use authentication for outgoing mail, and always use encrypted connections (SSL/TLS). 

These settings ensure secure sending and prevent authentication failures. 

TIP

You can double-check your email settings via your cPanel or Windows Plesk Control Panel to ensure you have the correct settings for you.

4: Confirm SMTP Authentication Is Enabled 

SMTP authentication must be enabled to send email. 

Look for a setting similar to: 

  • My outgoing server requires authentication 

If this option is disabled, sending will fail. 

5: Check SMTP Port Settings 

Recommended settings:

Security Port 
TLS / STARTTLS 587 
SSL 465 
Non-encrypted 25 (not recommended) 

Incorrect ports are one of the most common causes. 

TIP: If port 25 fails, change to 587. 

6: Update SMTP Settings in Your Email Client (as required) 

Most email applications allow SMTP port, encryption, and authentication settings to be updated in the Advanced Mail Settings section. Once you’ve made any changes, you can test to determine if you are still unable to send emails or if it succeeds.

We’ve provided quick instructions for different email clients below.

Microsoft Outlook 2002 / 2003 
  1. Open Outlook 
  2. Click Tools → E-mail Accounts 
  3. Select View or change existing e-mail accounts 
  4. Click Next 
  5. Select your email account 
  6. Click Change 
  7. Click More Settings 
  8. Open the Advanced tab 
Microsoft Outlook 2007 
  1. Open Outlook 
  2. Click Tools → Account Settings 
  3. Select the email account 
  4. Click Change 
  5. Click More Settings 
  6. Select the Advanced tab  
Microsoft Outlook 2010 
  1. Open Outlook 2010 
  2. Click Account Settings 
  3. Select your email account 
  4. Click Change 
  5. Click More Settings 
  6. Open the Advanced tab   
Microsoft Outlook 2013 
  1. Open Outlook 2013 
  2. Click Account Settings 
  3. Select your email account 
  4. Click Change 
  5. Click More Settings 
  6. Click the Advanced tab   
Outlook Express 5.x / 6.0 
  1. Open Outlook Express 
  2. Click Tools → Accounts 
  3. Select the Mail tab 
  4. Select your email account 
  5. Click Properties 
  6. Open the Advanced tab   
Windows Live Mail (2008 / 2009 / 2011) 
  1. Open Windows Live Mail 
  2. Click Accounts 
  3. Click Properties 
  4. Select the Advanced tab 
  5. Update the SMTP port and security settings   
Mac Mail 
  1. Open Mail 
  2. Click Mail → Preferences 
  3. Select Accounts 
  4. Choose your email account 
  5. Click Server Settings 
  6. If you do not see Server Settings: 
    • Open the server dropdown 
    • Click Edit Server List 
    • Select the Advanced tab    
iPhone / iOS Mail 
  1. Open Settings 
  2. Tap Mail → Accounts 
  3. Select your email account 
  4. Tap Account 
  5. Scroll to Outgoing Mail Server (SMTP) 
  6. Tap SMTP 
  7. Select the Primary Server 
  8. Update the SMTP server settings 
  9. Tap Done to save changes 
Mozilla Thunderbird 
  1. Open Thunderbird 
  2. Click Edit → Account Settings 
  3. Select Outgoing Server (SMTP) 
  4. Select the SMTP server to modify 
  5. Click Edit 

For full guides specific to your email client, you can explore more here. 

7: Check for Port 25 Blocking 

Many Internet Service Providers block port 25 to prevent spam.

  • If your email client uses port 25, sending may fail.  

Attempt to change the SMTP port to: 

587 (recommended) 
or 
465 (SSL) 
8: Restart Your Email Client 

After verifying and changing settings: 

  • Send a test message 
  • Save configuration 
  • Restart the email application 

                Advanced (Optional) Fixes (For Technical Users) 

                Administrators, or Technical Users, can perform additional diagnostics if sending issues persist. 

                1. Check SMTP Connectivity 

                Test connection to the SMTP server: 

                telnet mail.yourdomain.com 587 

                A successful connection returns: 

                220 mail.server.com ESMTP 
                2. Verify Firewall Rules 

                Ensure outbound connections allow the following SMTP ports: 

                • 25 
                • 465 
                • 587 

                Blocked firewall rules can prevent SMTP connections. 

                3. Verify Server Authentication Logs 

                Check mail logs for: 

                • authentication failures 
                • smtp connection timeouts 
                • relay denied 

                Example location: 

                /var/log/exim_mainlog 
                4. Confirm Email Routing 

                Incorrect routing settings may cause sending issues. 

                Verify routing configuration: 

                The correct setting depends on your email hosting environment. 

                Before You Move On  

                Confirm the following:  

                • SMTP authentication is enabled 
                • The correct outgoing server is configured 
                • The SMTP port is set to 587 or 465 
                • The email password is correct 
                • A test email was successfully sent 

                If This Didn’t Work 

                Try these additional checks: 

                • Send an email from Webmail 
                • Test from another device 
                • Temporarily disable the firewall 
                • Reset email account password 
                • Re-add the email account in your client 

                If the issue continues, contact support and include: 

                • Error message 
                • Timestamp 
                • Sender email address 
                • Device or email client used 

                Common Mistakes to Avoid 

                Most sending failures occur because: 

                • SMTP authentication disabled 
                • Wrong SMTP port used 
                • Outgoing server incorrect 
                • Password outdated 
                • Port 25 blocked 

                Correcting these resolves most issues. 

                Empowering Insight 

                Empowering Insight

                Email delivery relies on separate send and receive systems. 
                 
                Fixing the outgoing SMTP settings usually restores email sending in minutes. 

                If sending still fails, review these error codes: 

                • SMTP 535: Authentication Failed 
                • SMTP Error 421: Temporary Server Error  
                • SMTP Error 554: Transaction Failed 

                FAQs 

                Q. Will I lose my emails? 

                No, stored emails remain safely on the server. 

                Q. Why can I receive emails but not send them?  

                Receiving uses IMAP/POP, while sending uses SMTP. These systems operate independently. 

                Q. Can I undo these changes? 

                Yes, email client settings can be changed or reset anytime. 

                Additional Resources 

                A Guide to SMTP Error Codes
                Understanding SMTP Ports and SSL/TLS Encryption
                Recommended Server Settings for Email (Encryption & Ports)  
                Settings to Configure Email Accounts Across Devices
                Why Emails Bounce Back, Error Messages and How to Fix Them

                Need Additional Support? 

                We’re Here to Help: 

                Diagnosing why you are unable to send emails while receiving is fine, and how to fix this doesn’t have to feel technical with this easy-to-reference guide. Stuck? Check out our Scope of Support, and then contact our Support Team for further clarity and guidance (https://1grid.co.za/contact-us/). We’re ready to see how we can help! 

                Updated on March 11, 2026
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