email | Peter Viola

Using Asp.Net to Process NDR Emails

ASP.NET, Email Comments Off

Dec 172017

If you’ve ever managed a mailing list or sent out an announcement to a distribution group then you have inevitably experienced non-delivery report (NDR) floods. These messages indicate delivery problems for your some of your recipients. In most cases the delivery issues are straight forward such as the mailbox no longer being valid. Investing time to track down an end user’s new email address is time consuming and unrealistic if you have thousands of addresses on your list. So the simple solution is to remove them. Again if you have a large list then removing them manually will be a considerable time investment so why not leverage some Asp.net and automate it.

Process NDR messages with ListNanny

In a previous blog post I showed how you can remove spam messages using the Asp.net components aspNetPOP3 and aspNetMime by advancedintellect.com. It turns out they also have a fantastic component for processing NDR messages called ListNanny. So in the example below I have quite a few delivery failures that need processing.

When using ListNanny the first step of your program should be importing the latest NDR definition file provided by AdvancedIntellect.

string defPath= "c:\\ndr.def.xml"; 
NDR.ImportDefinitionFile( defPath );

1 2	string defPath= "c:\\ndr.def.xml"; NDR.ImportDefinitionFile( defPath );

Next you’ll connect to the mailbox containing the NDR messages, iterate through them, identify the bounced email address and then delete the bounced message. In my example below I have have a separate function to remove the bounced address from my list but I won’t cover that.

    POP3 pop = new POP3(mailserver, userid, password);
    pop.Connect();
    int messageCount = pop.MessageCount();
       
        for (int i = 0; i < messageCount; i++)
        {
            string messageText = pop.GetMessageAsText(i);
            NDR ndrMessage = NDR.Parse(messageText);
            ndrEmail = ndrMessage.BouncedEmailAddress;

            RemoveNDREmail(ndrEmail);
            pop.Delete(i);
        }

        pop.CommitDeletes();
        pop.Disconnect();

POP3 pop = new POP3(mailserver, userid, password);

pop.Connect();

int messageCount = pop.MessageCount();

for (int i = 0; i < messageCount; i++)

{

string messageText = pop.GetMessageAsText(i);

NDR ndrMessage = NDR.Parse(messageText);

ndrEmail = ndrMessage.BouncedEmailAddress;

RemoveNDREmail(ndrEmail);

pop.Delete(i);

}

pop.CommitDeletes();

pop.Disconnect();

Depending on how you send out your announcements you may receive a non-delivery report that references multiple bounced email address. If that is the case you can use the example below to process the NDR and identify each individual recipient from the group that needs to be removed.

NDR ndrMessage = NDR.Parse(messageText);
ndrEmail = ndrMessage.BouncedEmailAddress;       
DSN dsn = ndrMessage.FindDSN();

         if (dsn != null)
         {
             foreach (object recip in dsn.RecipientCollection)
             {
                 DSNRecipient dr = (DSNRecipient)recip;
                 if (dr.FinalRecipient != null)
                 {
                    ndrEmail = dr.FinalRecipient.Value;
                 }
             }
         }

NDR ndrMessage = NDR.Parse(messageText);

ndrEmail = ndrMessage.BouncedEmailAddress;

DSN dsn = ndrMessage.FindDSN();

if (dsn != null)

{

foreach (object recip in dsn.RecipientCollection)

{

DSNRecipient dr = (DSNRecipient)recip;

if (dr.FinalRecipient != null)

{

ndrEmail = dr.FinalRecipient.Value;

}

In Summary

Managing non-delivery report (NDR) emails can be a challenge when you need to prune stale emails from your mailinglist. Fortunately the folks at advancedintellect.com have a great asp.net component called ListNanny which can help automate processing your NDR messages and minimize future bounce emails. Thanks for reading!

Peter Viola

Creative, customer focused, results oriented, Senior Web Systems Engineer who enjoys providing the highest level of customer service supporting complex Windows hosting solutions. MCITP, MCSA, MCTS

Using Asp.net to Remove Spam And Keep Good Mail

ASP.NET, Email Comments Off

Nov 142017

Recently I was cleaning up a personal mailbox I’ve kept over the years for use when a 3rd party asks for an email address and I don’t want to provide my primary one. In these situations I prefer to give an address that I don’t frequently use because I know eventually I’ll start getting targeted unsolicited mail i.e spam from them. Ordinarily when cleaning out these mailboxes I would just purge it all however on this particular occasion I needed to keep some of the legitimate mail that was mixed in with the spam. I decided to do what any good programmer would do so I fired up some C# to surgically remove the spam.

Read Email Using POP3 With ASP.NET

When I initially checked my mailbox online I could see 3,900 unread messages waiting for me but it was obvious much of this was just marketing nonsense about 4K TVs, insurance quotes, limited time offers, and everything else you can imagine.

POP3 and IMAP are protocols used by mail clients to login to mailboxes and manage the messages contained in the mailbox. To perform this programmatically using Asp.net I decided to leverage aspNetPOP3 and aspNetMime by Dave Wanta at www.advancedintellect.com. These components make it easy to login to a mailbox with just a few lines code. At first I’m just going to download the message subjects into an array to identify the most repeat offenders. After sorting the array with the subjects I write it to a file.

POP3 pop = new POP3("server", "username", "pw");
            pop.Connect();
            int messageCount = pop.MessageCount();

            var subjects = new string[messageCount];

            for (int i = 0; i &lt; messageCount; i++)
            {
                try
                {
                    aspNetMime.MimeMessage msg = pop.GetMessage(i);
                    subjects[i] = msg.Subject.Value;
                }
                catch
                { }
            }
               

            var subjCounts = subjects.GroupBy(z =&gt; z);
            foreach (var group in subjCounts)
                activityLog(group.Key+ " -&gt; "+ group.Count());

            pop.Disconnect();

POP3 pop = new POP3("server", "username", "pw");

pop.Connect();

int messageCount = pop.MessageCount();

var subjects = new string[messageCount];

for (int i = 0; i < messageCount; i++)

{

try

{

aspNetMime.MimeMessage msg = pop.GetMessage(i);

subjects[i] = msg.Subject.Value;

}

catch

{ }

}

var subjCounts = subjects.GroupBy(z => z);

foreach (var group in subjCounts)

activityLog(group.Key+ " -> "+ group.Count());

pop.Disconnect();

Looking through the file it’s easy to see how much junk there is in the mailbox. Here is just a sample:

I will manually edit the file so that it only contains the message subjects that I want to delete. In the next part of the program I log back into the mailbox and loop through each message again and compare message subject to the subjects contained in the blacklist file. If it matches then the message is marked for deletion. After the program loops through all the messages the last command is to commit the deletes. Afterwards I will log back into the mailbox online and see how the inbox looks. If it feels like there’s still too much spam then I’ll go run the program again using a new batch of subjects.

  string[] subjectsArr = File.ReadAllLines(Directory.GetCurrentDirectory() + @"\subjects.txt");

            POP3 pop = new POP3("server", "username", "pw");
            pop.Connect();
            int messageCount = pop.MessageCount();

            for (int i = 0; i < messageCount; i++)
            {
                aspNetMime.MimeMessage msg = pop.GetMessage(i);
                foreach (string spamKeyword in subjectsArr)
                    if (msg.Subject.Value.Contains(spamKeyword))
                    { 
                        pop.Delete(i);
                        break;
                    }
            }
      
            pop.CommitDeletes();
            pop.Disconnect();

string[] subjectsArr = File.ReadAllLines(Directory.GetCurrentDirectory() + @"\subjects.txt");

POP3 pop = new POP3("server", "username", "pw");

pop.Connect();

int messageCount = pop.MessageCount();

for (int i = 0; i < messageCount; i++)

{

aspNetMime.MimeMessage msg = pop.GetMessage(i);

foreach (string spamKeyword in subjectsArr)

if (msg.Subject.Value.Contains(spamKeyword))

{

pop.Delete(i);

break;

}

pop.CommitDeletes();

pop.Disconnect();

In Summary

Sometimes it’s necessary to manually clean up the spam from a mailbox rather just purging everything. Using aspNetPOP3 and aspNetMime from www.advancedintellect.com it’s easy to create an asp.net program to identify and delete only the spam messages from your mailbox while keeping the good mail. Thanks for reading!

Peter Viola

Creative, customer focused, results oriented, Senior Web Systems Engineer who enjoys providing the highest level of customer service supporting complex Windows hosting solutions. MCITP, MCSA, MCTS