全新安装的iRedMail可接收邮件但无法发送

Hey there, let's work through this issue step by step—since you can receive external emails but can't send to Gmail or Yahoo, the problem almost certainly ties back to deliverability checks those large providers enforce. Here's what to prioritize checking:

1. Validate SPF, DKIM, and DMARC DNS Records #

Big email services reject or flag emails that lack proper authentication records. These are non-negotiable:

• SPF Record: Run dig yourdomain.com TXT in your server's terminal. Look for a record starting with v=spf1 that includes your server's public IP (e.g., v=spf1 ip4:192.168.1.1 -all). If it's missing or incorrect, add/update it in your domain's DNS settings.
• DKIM Record: iRedMail auto-generates a DKIM key during installation. Use amavisd-new showkeys to view your domain's DKIM configuration. Compare this to the TXT record in your domain's DNS—they must match exactly. If not, update the DNS record.
• DMARC Record: Add a DMARC TXT record to your domain (e.g., v=DMARC1; p=quarantine; sp=quarantine; rua=mailto:dmarc@yourdomain.com). This tells providers how to handle unauthenticated emails from your domain, which helps build trust over time.

2. Confirm Reverse DNS (PTR) Record #

Gmail and Yahoo require a valid PTR record that maps your server's IP back to your mail server hostname (e.g., mail.yourdomain.com):

• Log into your Vultr dashboard, navigate to your server's details, and locate the PTR record setting. Set it to match your mail server's fully qualified domain name (FQDN). Without this, your emails will almost certainly be rejected.

3. Check Server Hostname and Postfix HELO/EHLO Settings #

Ensure your server's hostname matches what Postfix uses for HELO/EHLO communications:

• Run hostname -f to get your server's FQDN—it should be something like mail.yourdomain.com.
• Open /etc/postfix/main.cf and verify the myhostname value matches this FQDN. If not, update it, then restart Postfix with systemctl restart postfix.

4. Analyze Mail Logs for Specific Errors #

The logs will tell you exactly why delivery is failing. Run these commands to spot issues:

• Tail live logs: tail -f /var/log/mail.log
• Search for rejection messages: grep -i "reject\|fail\|error" /var/log/mail.log
  Common errors include:
  • 550 5.7.1 Unauthenticated email is not accepted: Missing or invalid SPF/DKIM records.
  • 554 5.7.1 Service unavailable: Invalid PTR record or blacklisted IP.

5. Check for IP Blacklisting #

New VPS IPs sometimes end up on spam databases. Use a free blacklist checking tool to see if your server's IP is listed. If it is:

• Request removal from the relevant blacklists.
• Contact Vultr support to see if they can assign you a clean, unlisted IP.

6. Verify Port 25 is Open #

Port 25 is required for outbound email delivery. Confirm it's accessible:

• Run telnet gmail-smtp-in.l.google.com 25 on your server. If you get a connection response (e.g., 220 mx.google.com ESMTP), the port is open.
• If not, check your server firewall with ufw status to ensure port 25 is allowed, and verify Vultr's cloud firewall settings don't block it.

Start with these checks—most delivery issues to major providers stem from one of these areas. Let me know what you find in the logs or DNS records, and we can troubleshoot further if needed.

内容的提问来源于stack exchange，提问作者ScioMind