What's Actually Happening

Emails are sent but not received by the recipient. Messages appear to be delivered but don't arrive in inbox.

The Error You'll See

  • Sender receives no bounce message
  • Email not in inbox or spam
  • Intermittent delivery issues

Why This Happens

  1. 1.Spam filter blocking
  2. 2.Mailbox full
  3. 3.MX record misconfigured
  4. 4.Greylisting delay
  5. 5.Blacklist issues

Step 1: Check MX Records

bash
dig MX example.com
nslookup -type=MX example.com

Step 2: Check Blacklists

bash
# Check if IP is blacklisted
dig @zen.spamhaus.org A 1.2.3.4.zen.spamhaus.org
# Or use online tools:
# https://mxtoolbox.com/blacklists.aspx

Step 3: Check Spam Folder

bash
# Ask recipient to check spam/junk folder
# Mark as not spam to train filter

Step 4: Check SPF/DKIM/DMARC

bash
dig TXT example.com | grep SPF
dig TXT default._domainkey.example.com
dig TXT _dmarc.example.com

Step 5: Test Delivery

bash
# Send test email with tracking
# Use tools like mail-tester.com

Step 6: Check Mail Server Logs

bash
tail -f /var/log/mail.log
grep "user@example.com" /var/log/mail.log

Step 7: Check Greylisting

bash
# Greylisting may delay delivery
# Wait 5-15 minutes for retry

Step 8: Check Mailbox Quota

bash
# Check if mailbox is full
# On mail server:
doveadm quota get -u user@example.com

Step 9: Check Email Headers

bash
# View full headers in email client
# Look for: Received, Authentication-Results

Step 10: Monitor Delivery

bash
# Watch mail logs during test:
tail -f /var/log/mail.log | grep -i "status=sent"
  • [Fix Email Sending Failed](/articles/fix-email-sending-failed)
  • [Fix Email Going to Spam](/articles/fix-email-going-to-spam)