Email stopped working on your Plesk server and you need to find out why fast. The challenge with Plesk email failures is that the problem can sit in any one of three independent layers: the Postfix MTA that handles message routing, the Amavis/SpamAssassin content filter that sits between Postfix and delivery, or an IP blacklist that causes remote mail servers to reject your outgoing messages silently.
This guide teaches you how to read Plesk mail logs to identify which layer is failing, then walks through the targeted fix for each cause.
Understanding Plesk's Mail Stack
Plesk's email system on Linux uses three components in sequence:
- Postfix — receives incoming messages and queues outgoing messages
- Amavis (port 10024) — content filter that passes messages through SpamAssassin and optionally ClamAV before delivery
- Dovecot — handles IMAP and POP3 access so mail clients can read delivered messages
When any of these three services fails or is misconfigured, email stops flowing. The failure mode looks different in each case, and reading the right log file tells you exactly which component is responsible.
Step 1: Read the Plesk Mail Log
All Plesk mail events are logged in one file:
tail -200 /var/log/maillogOn Ubuntu/Debian-based Plesk servers, the log may be at /var/log/mail.log instead.
Look for these key patterns that identify which layer is failing:
Amavis connection refused
delivery temporarily suspended: connect to 127.0.0.1[127.0.0.1]:10024: Connection refusedThis means Postfix tried to pass the message to Amavis for content filtering, but the Amavis service is not running. See Step 2.
SMTP authentication failure
SASL authentication failure: cannot connect to Dovecot: No such file or directory
warning: SASL: Connect to private/auth failed: No such file or directoryPostfix cannot reach the Dovecot auth socket. See Step 3.
Outbound rejection by remote server
550 5.7.1 Service unavailable; Client host [YOUR_IP] blocked using Spamhaus
554 5.7.1 [YOUR_IP] is not allowed to send from
Your server IP is on a DNS blacklist (DNSBL). The remote mail server is refusing your messages at the SMTP level. See Step 4.
Postfix queue backup
status=deferred (delivery temporarily suspended)
warning: queue file size limit exceededMessages are accumulating in the Postfix queue. See Step 5.
💡 None of these worked? Skip the guesswork.
Get Expert Help →Step 2: Fix Amavis Not Running (Port 10024 Connection Refused)
Amavis is the most common cause of total email failure on Plesk servers. When it crashes, Postfix cannot deliver any message — inbound or outbound.
systemctl status amavisIf it shows "failed" or "inactive", restart it:
systemctl restart amavisAlternatively, use Plesk's Service Management: Plesk → Tools & Settings → Services Management → find Amavis → click Restart.
tail -100 /var/log/amavis/mail.logCommon crash causes include corrupted SpamAssassin rules or a full disk. If Amavis crashes repeatedly within minutes of restart, check disk space:
df -h /var/spool/amavisAmavis spools messages to /var/spool/amavis. If this partition is full, clear old temp files:
find /var/spool/amavis/tmp -mtime +1 -deletenc -z 127.0.0.1 10024 && echo "Amavis port 10024 is open" || echo "Still closed"systemctl status dovecotIf Dovecot is not running:
systemctl restart dovecotls -la /var/spool/postfix/private/authIf this file is missing, the auth socket was not created by Dovecot — restart Dovecot to recreate it.
Plesk provides a built-in repair tool that checks and fixes mail configuration inconsistencies:
plesk repair mail -yThis command validates Postfix, Dovecot, and Amavis configuration files and resets them to correct values. It is safe to run on a live server — it does not delete mail data.
After a Plesk update, some servers hit this error in /var/log/mail.err:
postfix/smtpd fatal: no SASL authentication mechanismsFix it by re-enabling Cyrus SASL mechanisms:
postconf -e 'smtpd_sasl_auth_enable = yes'
postconf -e 'smtpd_sasl_type = dovecot'
postconf -e 'smtpd_sasl_path = private/auth'
systemctl restart postfixRun from the server to get its public IP:
curl -s ifconfig.meThen check that IP on MXToolbox Blacklist Check (mxtoolbox.com/blacklists.aspx) or run:
host -tA YOUR_SERVER_IP.zen.spamhaus.orgA response of 127.0.0.x means your IP is on the Spamhaus ZEN list. A NXDOMAIN response means it is clean.
Before requesting delisting, stop the outbound spam or you will be relisted immediately. Check the Postfix mail queue:
mailq | head -50Look for thousands of queued messages to external domains from a single account. To find the sending account:
grep "status=sent" /var/log/maillog | awk '{print $7}' | sort | uniq -c | sort -rn | head -20If one domain or user is responsible, suspend the mailbox in Plesk or run:
postsuper -d ALL deferredThis flushes the deferred queue — only run this after you have identified and stopped the spam source.
- Spamhaus — submit a removal request at spamhaus.org/lookup
- Barracuda — lookup.barracudacentral.org → request removal
- SORBS — Note: SORBS was shut down in 2024. If log entries mention SORBS, they can be ignored.
Blacklisters require these to be correct before approving a removal. Check rDNS for your IP:
dig -x YOUR_SERVER_IP +shortIt should resolve to your server hostname. Check SPF for your domain:
dig TXT yourdomain.com | grep spfPlesk can enable DKIM signing from Plesk → Domains → your domain → Mail Settings → enable DKIM.
Step 5: Clear a Stuck Postfix Mail Queue
If mail was flowing normally but has built up in the queue (e.g., after a temporary Amavis outage), the deferred messages need to be flushed once the underlying issue is resolved.
Check the queue size
mailq | tail -1Retry all deferred messages
postqueue -fWatch delivery in real time
tail -f /var/log/maillog | grep -E "status=sent|status=bounced|status=deferred"If you need expert diagnosis of persistent Plesk email delivery failures, CloudHouse Technologies provides managed Plesk server administration and resolves email issues quickly.