Possible causes of duplicate emails:

1) Microsoft Office Outlook 2003 Issues

This problem may occur if you use the Leave a copy of messages on the server option. This problem was first fixed in a hotfix that is now contained in a service pack. If you installed the latest Office 2003 service pack, you do not have to install the hotfix. Or, simply turn off the Leave a copy of messages on the server option. Note, you can find more information about this issues at http://support.microsoft.com/kb/885870

2) Share the same email address on two separate computers

In short, some email users are depending on the Leave a copy of messages on the server option to ensure each of them are getting a copy of the messages in their Inbox. Some have the issues persist even after upgrading their Outlook 2003. There is no quick fix to this issues. Alternatively, get another email address for each user. Or, have all email users use Webmail instead of email clients. Webmail does not download the email to your computer, thus bypass the need of using Leave a copy option.

Since eliminating the problem at its source is not feasible, the last resort is to remove duplicate email manually or using program like MapiLab’s Duplicate Email Remover.

3) Corrupt email message in your inbox on the mail server

If you are getting duplicate emails on your computer in your Outlook Express, it could be that there is a corrupt email message in your inbox on the mail server. To delete the corupt email, simply delete the corrupt/damaged message that is creating the duplicates. You can do it in by going to your Webmail.

4) Sync file error in outlook Express

The file which keep track of which messages are downloaded from the POP email server may have problem keeping the sync in order. Go to the Email Store Folder in your Outlook Express and remove the file named ‘Pop3uidl.dbx’ while the Outlook Express is closed. Turn on the Outlook Express after removal and a new ‘Pop3uidl.dbx’ will be created automatically.

5) Incomplete email downloading

Each time you press the Send & Receive button in your Outlook or Outlook Express, the email messages are downloaded from your POP email server to your computer. Interrupted Internet connection or large email download may cause the downloading process to timeout. The next time you press the Send & Receive button, it retrieves messages all over again.

6) Sender’s email client infected by Virus

Sometimes, the duplicate email problems are caused by the sender. The sender’s Outlook may have been infected by Virus and it us used to trigger Spam email messages unnoticed. Or, simply a looping sending process happens to a corrupted Outlook.

Why You Should Stop Using Streamyx Email?

We visited our customer this morning to do a CSI investigation on site.

Only to find out, there is an extra ‘:’ found in front of the email address used by the Sender. Looks Sender’s Outlook had appended this kidding fields into the email address after one press the Reply button.

Anyway, we are happy the problem solved :)

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Go to http://www.kitterman.com/spf/validate.html and enter your own domain name (do not enter ‘www’). The result shows if you have a SPF record. SPF fights return-path address forgery and makes it easier to identify spoofs.

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DNSreport started as a free tools to run your mail server against 100 over tests. The result is a full page report to tell you where goes wrong and why! Anyway, the full report is now stripped-down in the free service. Without subscribing to their paid service, users are able to view a summary of your test result. The result is layman-proof, check it out!

2) Is your mail server running on a small scale setup?

Check the IP address of your Webmail, POP, SMTP and Website. If all of them are identical, your mail server must have installed all these services in one server. Putting all eggs in one basket, bad ideas! You can use the web-based Dig tools from Geektools!

3. Is your mail server hosted in just one or multiple data centre?

Again, based on the Dig tools, you can tell if most of the IP address are in the same class (only the last set of numbers are different). If they are, chances they are in the same data centre. Geographically-dispersed data center provides higher availability support.

4. Do you have a Reverse DNS?

It is not end of the world if you don’t’ Anyway, having one means you email are less likely to be marked as Spam! Use AOL Postmaster’s Reverse DNS Check.

5. The recipient’s email address has some problems, how to verify?

Use Free Email Address Verifier. This email verification tool actually connects to the mail server and checks whether the mailbox exists or not.

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The following report shows the uptime in percentage, total outage and total downtime. The measurement is able to reflect how reliable is a web host in Malaysia.

It is easy to say that Jaring data centre or Streamyx broadband connection is down and causes your email problem. Isn’t that email service provider should be the best person to decide which is the best data centre for their customers?

What’s your story? Share with us by posting it as comment below.

DNS Check

If the result returned no valid hostname of your mail server, please inform the service provider of your IP address to request this setup to be done. Without this, outgoing email from your mail server can be marked as Spam as your IP address is not resolving to a valid hostname.

“When you register a domain name with a domain registrar, you usually become responsible for that Forward DNS domain. In DNS terms, the domain is delegated to you. However, you are not also responsible for your reverse records. Your Reverse DNS records are still most likely to be the responsibility of your hosting facility or ISP. To make changed to your Reverse DNS PTR records, you must contact the company where you get your IP addresses from, usually a hosting facility or an ISP.”

Extracted from http://www.tech-faq.com/reverse-dns.shtml

Of course, you can safelist/whitelist that particular email address so that it will not be marked as Spam in future. But, this does not solve the problem forever, and it works to your mail server only.

To know why, check the header of the Spamm’ed mail. In Outlook Express, right click on the email and view the Message Properties. Find the line which contains the score of your Spam. Usually, anything more than 6 are marked as Spam. Higher marks means this email do not pass most of the Spam tests.

If you are keen on what test the email failed, check this out