Email not sending-troubleshooting outgoing email
Diagnose why email is not sending from your domain or mail client. Covers SMTP authentication, port blocks, sending limits, SPF issues, and blacklisted IPs.
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When email stops sending, the cause is usually one of four things: wrong SMTP settings in your mail client, a blocked port, a sending limit reached, or a blacklisted IP. Work through this guide step by step to find and fix the problem.
Mail client not sending
First, test whether the issue is your mail client or the server. Log in to webmail (https://yourdomain.com/webmail) and try sending from there. If email sends from webmail but not your client, the client configuration is the problem.
SMTP settings and authentication
Verify your mail client's SMTP settings match these values:
| Setting | Value |
|---|---|
| SMTP Server | mail.yourdomain.com |
| Port | 465 (SSL) or 587 (STARTTLS) |
| Encryption | SSL/TLS or STARTTLS |
| Username | Your full email address |
| Password | Your email account password |
| Authentication | Required (Normal password) |
Port 25 and port 587
Port 25 (the traditional SMTP port) is blocked on all shared hosting outbound connections. This is standard industry practice to prevent spam. Always use port 587 (STARTTLS) or 465 (SSL) for sending email through a mail client.
See Port 25 and email policy for more details.
PHP mail() not sending
If a contact form or script uses PHP's built-in mail() function and emails aren't being received, the issue is often a missing or invalid From header, or the server IP is blocked by the recipient's mail provider.
Better approach: configure your form to use SMTP instead of mail(). For WordPress, use the WP Mail SMTP plugin and point it to your UnderHost email account credentials. For other PHP scripts, use PHPMailer or Swift Mailer libraries with SMTP authentication.
Contact forms using SMTP with proper authentication have much better deliverability than plain PHP mail(). Most spam filters trust SMTP-authenticated email more than server-generated mail.
Sending limits
Shared hosting plans have email sending rate limits to prevent abuse. If you're sending bulk newsletters or automated emails, you may hit these limits. Signs:
- Emails start failing after sending a certain number
- Error: "Relay access denied" or "Message quota exceeded"
For bulk sending, use a dedicated email delivery service (Mailgun, Amazon SES, SendGrid) rather than sending through your hosting account's mail server.
IP blacklist check
If your server's IP is on a major spam blacklist, outgoing email may be rejected by recipient servers. See Email blacklists-check and delist your IP to check your status and follow removal instructions for each blacklist.
Important: identify and stop what caused the listing first (compromised WordPress, a sending script, weak email passwords). If you don't fix the root cause, the IP will be relisted.
Related: How to set up email accounts in cPanel | Email blacklists-check and delist your IP or domain | Understanding email bounce messages | Configuring email in Outlook, Thunderbird, and Apple Mail
Need email hosting?
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