Multiple copies of same email in outlook! Prevent receiving!

To prevent receiving multiple copies of the same email in outlook we need to know the fact behind it. There are few possible reasons for receiving multiple copies of the same email in outlook. At the same time we will also try for the possible resolutions.

Prevent receiving multiple copies of the same email in Outlook 

 

1.   SYNCHRONIZATION of POP SERVERS

      If you set to "leave messages on the server" in your e-mail client (Outlook) then Outlook has to be remember what messages it has downloaded. The server never "remember" which message you downloaded, this is why you can download messages at the office, leave them on the server and download them again at home. If the server remembered which messages had been downloaded, then they would not download again to another machine. Each instance of Outlook on each machine must "remember" what it has already downloaded. 
  
In order to remember which messages it has downloaded, Outlook keeps a list of the "message IDs" for the messages it has downloaded. When Outlook checks for new messages, it gets a list of the entire message IDs on the server, compares it to the list or message IDs it has downloaded, and requests the messages it does not have. 

If the list of downloaded message IDs becomes corrupted, which is common especially when that list gets long, Outlook will "lose track" and start downloading all messages over and over again.
  
RESOLUTION: Un-check "leave messages on the server" and then "Send and receive" to get the mailbox cleaned out. You can then re-check it. We suggest you only leave messages on the server for 10 or 15 days, depending on your mail usage. 

2.     E-MAIL CAN GET STACK IN MAIL SERVER

An email message can get stuck in your inbox on your server. This can cause your send / receive session to terminate without updating your list of received messages, or without deleting received messages from the server.

Messages can get stuck when; (a) they are corrupted or crafted to contain special characters that cause your mail program to terminate, (b) large messages take so long to send or receive that your mail program starts another send / receive process before that last is completed, or (c) large messages take so long to send or receive that you interrupt the process before it's complete.

RESOLUTION: Log into your mail account with Web Mail and move the messages in your inbox to a temporary folder. Then start moving messages back to your inbox one or a few at a time and downloading them to Outlook until you find the message causing the problem. Manage problem messages in Web Mail, and move them to a temporary folder or delete them.
 

3.     SEND/RECEIVE SESSION/CYCLE

Your e-mail client is automatically checking for new e-mail, too often. Some users have their e-mail client set to check as frequently as every minute. Checking more frequently than every 10 to 15 minutes can result in the next check beginning before the last one has ended. When that happens, the index file of the e-mail client will no longer be synchronized with the e-mail server, resulting in multiple copies of the same message. Do the following to correct his issue:

RESOLUTION: Change the setting of your e-mail client so that it automatically checks for new e-mail no more frequently than every 15 minutes. You can manually force a check if needed, but be sure the last check has completely finished.
 

4.     USING MULTIPLE EMAIL CLIENT

Another e-mail client may be checking your mailbox while you are checking it. There are hundreds of free/shareware/ActiveX controls/Java applets that can check mailboxes for new messages. A quick check shows that ICQ, 3 different freeware utilities, AOL Instant Messenger, Yahoo and Netscape Notified all start POP sessions to check for new mail. All could cause the same results with either POP or IMAP or with mail left on the server. The best solution is not to use these utilities. One can also cause the problem by using Web Messaging while another e-mail client is logged in to the same mailbox.

RESOLUTION: Use only one program to check your mail box ant any one time.

                                                                                               

5.     SMTP TIMEOUT

        

    The other reason for recipients to receive multiple copies of the same email message is if the recipient mail server does not respond quickly enough to the sender server. As a result, the sender server attempts to resend the email message at intervals until the message is accepted by the recipient mail server. At times when a mail server is overloaded or busy it may not accept new messages immediately.

RESOLUTION: This issue is usually a temporary issue that should go away. Unfortunately there is nothing that you can do to prevent this.

           

6.  NETWORK AND SERVER PROBLEMS

If you are receiving duplicates of only some of your mail, the cause may be technical difficulty along the delivery path. Either a network connection is having problems, or one of the computers along the route is very slow or having other system problems.

Most mail delivery protocols and programs are conservative. If they are unsure whether a mail message was successfully passed along to the next computer on the network, the sender will try to send it again. If the message was passed along successfully the first time, the second attempt will produce a second copy of the same message, and you will likely receive both copies.

On large networks such as the Internet, a mail message must usually pass through several different computers before it reaches its final destination. This problem can potentially occur at any computer along the way.

A synchronization problem in the SMTP mail delivery protocol, which is used by most mail programs on the Internet, can make this error more likely; see the Internet RFC document Duplicate Messages and SMTP .

RESOLUTION: Unfortunately, there is no real solution to this, except to wait until the problem on the network is resolved. If this problem is chronic and doesn't seem to be associated with a more general network or computer problem, the mail delivery software on the computer in question may be miss-configured. In this case, contact the administrator of the computer.

7. RULES 

Rules and more specific "Move to folder" rules is the most easiest one to get yourself some duplicates. This is because for each e-mail received Outlook will fire all configured rules against it. The following example will show this can lead to duplicates.

In this example there are two rules configured;

1.  Apply this rule after the message arrives 
from Robert Sparnaaij 
move it to the Outlook folder

2. Apply this rule after the message arrives 
with Outlook in the subject 
move it to the Outlook folder

Now imagine that you receive an e-mail from me where I have the word Outlook in the subject; both rules with apply! So it will get moved two times creating a duplicate.

RESOLUTION: The way to prevent this is to add the action "stop processing more rules" to the rule. If we would add that action to the first rule and the rule applies the action "stop processing more rules" will prevent that the second rule will be executed. Keep in mind that if you have even more rules configured that should always trigger -for instance that assigns messages to a category or marks it for follow up- you’ll need to sort your rules in the correct order as well.

8. VIRUS SCANNER / FIREWALL

Another quite common evil which will end up creating duplicates are virus scanner that integrate with Outlook or too strictly configured firewall. To understand this I’ll explain a little bit how the e-mails are actually being received without a virus scanner or firewall;

When Outlook does a Send/Receive it will make a connection with the mail server and will ask the server which e-mails it is currently storing. The mail server will respond with a list and Outlook will verify with its local list if it has collected all the e-mails already. If so; Outlook will close the connection to the mail server. If not; Outlook will request the new e-mails from the server and when it has received all the e-mails it will close the connection with the mail server and update its own list of received e-mails.

The above illustrates a perfect Send/Receive cycle. If for some reason the connection gets terminated unexpectedly so that Outlook cannot close the connection to the mail server properly Outlook will consider it as a failed Send/Receive cycle and will not update its own list of received e-mails even when some or all of them have been received already. This means that at the next Send/Receive interval Outlook will check for new e-mails with an "outdated" list and collects the e-mails from the previous Send/Receive interval again and will not update its local list until the connection to the mail server closes properly.

This is where the virus scanner and firewall come into the picture. The exact method depends a bit on the virus scan solution chosen but basically when a virus scanner integrates with Outlook it will "intercept" the Send/Receive request from Outlook. So when Outlook does a Send/Receive and "thinks" it is talking to a mail server it is in fact talking to the virus scanner. This means that now the virus scanner is responsible for the connection. This means setting up the connection, requesting the list of mails stored on the server, managing the timeouts, etc… but also closing the connection properly and telling this to Outlook. Although this could go right of course many many times, keep in mind that you do have added a single point of failure to the Send/Receive process leaving you with another possibility that the connection to the mail server isn’t closed properly and already received e-mail being received again at the next Send/Receive interval.

RESOLUTION: Therefore it is another good reason to prevent your virus scan solution to integrate with Outlook. There is no direct need to integrate a virus scanner with Outlook as it is redundant anyway; it won’t add another level of security since it is one and the same tool as your on-access-scanner. Default Outlook security settings and an up-to-date virus scanner are enough to keep you safe! See the documentation of your virus scanner on how to disable its integration with Outlook.

Now that you know how the Send/Receive interval works you can imagine that a too strictly configured firewall could terminate the connection prematurely so Outlook will never have the chance to update its local list of received e-mails. In this case check/disable your firewall and wait two Send/Receive intervals. If the second one doesn’t cause any duplicates you’ll know that your firewall isn’t properly configured. See the documentation of your firewall software on how to configure your firewall for e-mail retrieval with Outlook.

9. PROFILE RECREATION

When you recreate your mail profile -for instance when the original got corrupted or when you reinstalled your PC and configure Outlook for the first time again- and you originally had Outlook configured to leave a copy on the server (POP3 account) it will collect all the e-mails from the server again even when you have received them in a previous configuration. This is because the newly created profile doesn’t "know" that these messages have been received before by another profile. So this means that when you recreate your mail profile and during setup you immediately configure it to use your old pst-file as the default delivery location it will create duplicates for the messages that are already received and that are still on-line as well.

RESOLUTION: To prevent this from happening make sure start Outlook at least once with a clean pst-file before reconnecting the old one and setting it as the default delivery location. This way you’ll collect all the e-mails in a new pst-file.

For Outlook 2002/XP and 2003

1.  Connect to your original pst-file by File-> Open-> Outlook Data File… and once opened move all the newly received e-mails to that pst-file.

2. Close Outlook and go to Control Panel-> Mail-> button Data Files…-> button E-mail Accounts-> button Next-> at the bottom you can select the original pst-file as the default delivery location and press Finish.

3. Press the button Data Files… and remove the other pst-file. If you want to keep your computer clean press the Settings button first and write down the location of the pst-file so you can physically delete the file as well and not just the connection to it.

For Outlook 2007

1.  Connect to your original pst-file by File-> Open-> Outlook Data File… and once opened move all the newly received e-mails to that pst-file.

2. Close Outlook and go to Control Panel-> Mail-> E-mail Accounts-> tab Data Files. Select the the original pst-file and press Set as Default

3. Select the other pst-file and press Remove. If you want to keep your computer clean press the Settings button first and write down the location of the pst-file so you can physically delete the file as well and not just the connection to it.

For Outlook 2010 
Outlook 2010 does remember which emails have been downloaded before as it stores this information in the pst-file itself.

Upon configuring your account, you can specify the delivery location to an already existing pst-file instead of letting Outlook create a new one for you. If you have retrieved your account settings via AutoDiscover, you can select the option to manually configure you account. This will get you to a screen where the account settings retrieved via AutoDiscover are shown and also has a section “Deliver new message to” to select your original pst-file.

To change the delivery pst-file for your account after you have configured your account use; 
File-> Account Settings-> Account Settings-> select your e-mail account-> button Change Folder-> select New Outlook Data File… and browse to your original pst-file.

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