Nagios XI Email Notifications with Zoho Mail SMTP: 2025 Guide

This guide walks you through configuring Nagios XI to send email notifications with Zoho Mail using secure SMTP (TLS) and a Zoho app password, with step-by-step settings, verification, and quick fixes for common errors.

Prerequisites

1. Zoho Account: Must have two-factor authentication enabled (if using app password) or a valid account password.
2. Zoho App Password: A 16-character code generated specifically for “Nagios XI” (required for 2FA-enabled accounts).
3. Nagios XI Admin Access: Ensure the XI server has outbound network access to smtp.zoho.com or smtppro.zoho.com on ports 587 and/or 465.
4. Time Synchronization: The XI server must use NTP for accurate time sync to prevent TLS handshake issues.

Step 1: Enable Two-Factor Authentication and Generate a Zoho App Password

1. Login to your Zoho Mail account at Zoho Account Security.
2. Navigate to Security → Two-Factor Authentication and enable it if you plan to use an app password.
3. Under Application-Specific Passwords, click Generate App Password, select “Mail” as the app, enter “Nagios XI” as the label, and click Generate.
4. Copy the 16-character password displayed and store it securely for use in Nagios XI. Ensure no extra spaces are copied. If 2FA is not enabled, you may use your regular Zoho account password instead.

Tip: If the Application-Specific Passwords option is not visible, confirm 2FA is enabled, sign out and back in, or ensure you’re using the correct Zoho data center portal (e.g., zoho.com, zoho.eu). If app passwords are unavailable or you prefer not to use 2FA, use your account password, but note this is less secure. For paid organization accounts, ensure the email address matches the account or alias.

Step 2: Configure SMTP Settings in Nagios XI

1. Log into Nagios XI as an administrator and navigate to Admin → System Config → Email Settings.
2. Update the Send Mail From field from the default root@localhost to Nagios Alerts <[email protected]> (replace with your Zoho email address or domain-based email for paid accounts).
3. Select Mail Method: SMTP.
4. Configure the following SMTP Settings:
   • Host: smtp.zoho.com (personal/free accounts) or smtppro.zoho.com (paid organization accounts)
   • Port: 587
   • Security: TLS (recommended; SSL on port 465 is also supported)
   • Username: Your full Zoho email address (e.g., [email protected] or [email protected])
   • Password: The 16-character app password from Step 1 (or account password if 2FA is disabled)
5. Enable Mail Logging and Debugging to write detailed logs to /usr/local/nagiosxi/tmp/phpmailer.log.
6. Click Update Settings.

Step 3: Update User Email in Account Settings

1. In Nagios XI, click the user icon in the top-right corner and select Account Settings.
2. Update the Email Address field from the default root@localhost to the email address where you want to receive notifications (e.g., [email protected] or another preferred email).
3. Enter your current Nagios XI password to authenticate the change.
4. Click Update Settings to save the email address.

Step 4: Send a Test Email

1. Return to Admin → System Config → Email Settings.

2. Click Send A Test Email to verify the SMTP configuration.

3. Check the designated inbox to confirm the test email arrives. If it doesn’t appear, check the spam or junk folder.

Step 5: Test Notifications with a Real Alert

1. Assign the Zoho-backed contact to a test host or service in Nagios XI.
2. Trigger a test alert by forcing a soft problem state or using the Send Custom Notification feature.
3. Verify that the alert email arrives in the designated inbox. Check the spam or junk folder if it does not appear.

Troubleshooting

Symptom	Likely Cause	Solution
Relaying Disallowed or 535 Authentication failed	Mismatched email address or incorrect password.	Ensure the username matches the Zoho email or alias and use the app password (or account password if 2FA is disabled). Regenerate if necessary, ensuring no extra spaces.
Connection timeouts	Firewall blocking ports 587/465.	Allow outbound TCP 587 and/or 465 to smtp.zoho.com or smtppro.zoho.com.
TLS handshake or certificate errors	Outdated OpenSSL/CA bundle or time sync.	Update CA certificates, verify NTP sync, and retry with TLS on port 587.
Test email works; contacts get nothing	Legacy sendmail commands in use.	Switch affected contacts to XI PHPMailer notification commands.
Emails land in spam	Mismatched from domain or poor content.	Use the Zoho email in From, ensure meaningful subject/body, avoid URL-only emails. Verify SPF/DKIM for custom domains.

Conclusion

Nagios XI now delivers secure notifications through Zoho Mail using TLS and an app password. Keep NTP in sync, rotate the app password, and add SPF/DKIM for custom domains. After any change, send a test and review phpmailer.log to confirm delivery.

For further support, visit the Nagios Support Forum or the Nagios Documentation.