SmarterMail Not Receiving Email: Fix Failures in Minutes

Is your SmarterMail not receiving email? Don’t panic, as it is fixable! The common factors behind this are DNS misconfiguration, blocked SMTP ports, or mail service interruptions. Today, I’ll walk you through the causes and fixes step by step to resolve the SmartMail error, quickly and effectively.

Table of Contents

• Common Symptoms When SmarterMail Is Unable to Receive Email
• Major Reasons SmarterMail is Not Receiving Email
• Step-by-Step Troubleshooting Guide
• Advanced Fixes
• When I Recommend Contacting Hosting or ISP Support
• Author’s Verdict

Common Symptoms When SmarterMail Is Unable to Receive Email

Before exploring fixes, here’s what users usually notice when SmarterMail stops accepting incoming mail:

• Users aren’t getting new emails in the inbox.
• Receiving IMAP authentication failed message.
• People trying to email you get a bounce-back or error message saying the mail couldn’t be delivered.
• The mail queue looks empty, or messages seem stuck there without moving.
• Incoming messages take a long time to arrive or don’t show up at all.
• See errors like “connection failed” or “rejected” in SmarterMail’s logs.
• External senders say their emails keep getting delayed or lost.
• The SmarterMail webmail interface doesn’t show any new activity or recent mail.
• Your antivirus or firewall might be blocking mail connections without you realising it.
• The server CPU or memory usage may be higher than usual, which will affect mail delivery.

These signs usually mean something is wrong with your mail flow, and checking them early can save you a lot of time. Next, I’ll share the reasons behind it.

Related article: Archive IMAP Emails

Major Reasons SmarterMail Not Receiving Email

When I experienced this issue, I researched and found these factors led to this:

#1. DNS or MX Records Are Misconfigured

Incorrect MX records are one of the top reasons SmarterMail cannot receive emails. For the same, check:

• Make sure your domain’s MX record points to the right mail server where SmarterMail is hosted.
• Check that the MX record priority is set properly; lower numbers mean higher priority.
• Confirm that the A record points to your server’s correct IP address.
• If you recently changed any DNS settings, wait for DNS propagation to finish; it can take a few hours for the changes to update everywhere.

How to check why SmarterMail not receiving email?

You can use:

• nslookup -type=mx domain.com
• MXToolbox MX Lookup
• Dig command

If the MX record points to the wrong server, your emails won’t reach SmarterMail at all.

#2. IP Blacklisting or Reputation Issues

If you find that the server IP is blacklisted, many email providers will refuse the connection. In that case, check:

• MXToolbox blacklist check
• Spamhaus, Barracuda, SORBS, Proofpoint, and others

#3. SmarterMail Spool Service is Stopped

Sometimes the spool (mail queue) service stops working. To verify:

1. Log in to the SmarterMail admin dashboard
2. Go to Monitoring > Services
3. Ensure the spool service is running

#4. SMTP Binding Issues

SMTP might be bound to the wrong IP. Here’s what to check:

• Domain-level IP bindings
• Server-level IP bindings
• Conflicts due to multiple NICs or virtual adapters

#5. Anti-Spam or Security Rules Blocking Email

I find that inbound filtering is too restrictive and leads to SmarterMail not receiving email​ issues. Common problem areas to check:

• Greylisting rejects all first attempts
• DMARC or SPF hard fail will cause rejection
• Custom rules blocking legitimate senders
• Intrusion prevention accidentally bans a sender

#6. The Mail Queue Is Corrupted

If incoming messages “vanish”, spool corruption can be the reason. In that case:

• Check the spool folder integrity
• Look for orphaned .grp or .eml files
• Restart the spool service

Also read: How to Delete IMAP Emails from Server

#7. Disk Space Full

When the server runs out of disk space, SmarterMail cannot save new emails to the spool or user mailboxes. This leads to bounced or delayed messages. Senders may receive errors like 552 Disk full or Mailbox quota exceeded.

1. Check the current disk usage on the server.
2. Delete unwanted files that are no longer needed.
3. Increase mailbox or domain storage quotas if required.
4. Expand server storage if it often runs low.
5. Restart SmarterMail services once space is cleared.

But, if you don’t want to delete the data or upgrade the server storage, then I prefer to back up old emails locally and remove them from the server. This process ensures you can access the email file offline whenever you want. Moreover, having an offline replica ensures data continuity in accidental data loss or cyberattack scenarios.

For the same, I use the SysTools IMAP Backup Tool. It connects directly to SmarterMail using the IMAP protocol and lets me back up all my emails to the local system in formats like PST, EML, MBOX, MSG or PDF. 

This is helpful when you want to create a full copy of user mailboxes or move data between servers. So, download this solution now for free, and save your data locally. 

Step-by-Step SmarterMail Not Receiving Email Troubleshooting Guide

Here’s a quick step-by-step guide to troubleshoot the problems listed above:

#Step 1. Check DNS and MX Records

Use MXToolbox first to verify:

• MX record configuration
• DNS propagation
• SMTP response

If DNS is incorrect, fix it immediately because nothing else will work until this is resolved.

#Step 2. Test SMTP Port 25

Test connectivity using:

telnet mail.domain.com 25

If the server doesn’t respond, it usually indicates that:

• The firewall is blocking the port
• The ISP is blocking port 25
• The SMTP service is down

#Step 3. Review SmarterMail Logs

Check:

• SMTP In logs
• Delivery logs
• Spam check logs

These are extremely detailed and point directly to the cause.

#Step 4. Confirm IP Reputation

Run a blacklist check to see if the server IP is blocked. If blacklisted, take action such as:

• Requesting delisting
• Switching to a clean IP
• Configuring proper SPF, DKIM, and DMARC

#Step 5. Inspect Security Filters

Go to: Security > Anti-spam > Filtering

Now resolve SmarterMail not receiving email​ by, looking for:

• High spam thresholds
• Greylisting delays
• IP blocking rules

#Step 6. Restart SmarterMail Services

Restart:

• SmarterMail service
• Spool service
• IIS (if required)

#Step 7. Check the Spool

If emails are stuck:

• Inspect spool logs
• Look for malformed files
• Clear corrupt entries

Advanced Fixes to Resolve SmarterMail Not Receiving Email Effectively

If all the mentioned troubleshooting not work in your case, then try these advanced steps to fix the issue:

#1. Reverse DNS (PTR) Misconfigured

Many mail servers reject email without a valid PTR record. To fix, ask the hosting provider to set the PTR to: 

mail.domain.com

#2. SmarterMail Upgrade Causing Issues

After updates, some settings will reset. To verify:

• Bindings
• Services
• Spam profile compatibility

#3. SSL/TLS Issues

If TLS negotiation fails, the mail will be rejected. So verify:

• Certificate validity
• Cipher compatibility
• TLS settings in SMTP

#4. Disk Space Full

If the server runs out of space, new emails cannot be written to the spool. To resolve it, increase disk allocation or clear log files.

When I Recommend Contacting Hosting or ISP Support

I suggest contacting the provider if:

• Port 25 is blocked at the ISP level
• The server IP is repeatedly blacklisted
• DNS is controlled externally

Sometimes the issue lies outside SmarterMail entirely.

Author’s Verdict

When “SmarterMail not receiving email,” I’ve noticed that the root cause is always one of the following:

• DNS misconfiguration
• SMTP port blocking
• IP blacklisting
• Anti-spam filtering issues
• Service failures on the server

By following the step-by-step troubleshooting process I explained above, you can quickly identify and fix the problem with minimal downtime.