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ivan  
#1 Posted : Wednesday, April 13, 2011 5:08:56 AM(UTC)
ivan

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C#/CSharp Example

If you want to leave a copy of email on the server, you should not call Delete method. However, there is a problem, how can you know if the email has already been downloaded (read)? If there is a way to identify the downloaded email, you can avoid downloading the duplicated email from your POP3/IMAP4 server.

Every email has a unique identifier (UIDL) on POP3 server. POP3 UIDL is only unique in the email life time. That means if the email was deleted from the server, other email can use the old unique identifier. Another problem is: UIDL in POP3 server can be any number or characters, so we cannot use UIDL as the file name, because UIDL may contain invalid characters for file name.

To solve this problem, we have to store the UIDL to a txt file and synchronize it with server every time.

The following example codes demonstrate how to mark the email as downloaded/read on POP3 server.

Code:

// The following example codes demonstrate marking email as read/downloaded on POP3 server
// To get full sample projects, please download and install EAGetMail on your machine.
// To run it correctly, please change email server, user, password, folder, file name value to yours

using System; 
using System.Collections; 
using System.Collections.Generic; 
using System.Text; 
using System.IO; 

// Add EAGetMail namespace
using EAGetMail; 

namespace receiveemail 
{ 
    class MyMailClient 
    { 
        private string m_uidlfile = "uidl.txt"; 
        private string m_curpath = ""; 
        private ArrayList m_arUidl = new ArrayList(); 

        #region UIDL Functions 
        // uidl is the identifier of every email on POP3/IMAP4 server, to
        // avoid retrieve the same email from server more than once, we
        // record the email uidl retrieved every time if you delete the
        // email from server every time and not to leave a copy of email on
        // the server, then please remove all the function about uidl.
        private bool _FindUIDL(MailInfo[] infos, string uidl) 
        { 
            int count = infos.Length; 
            for (int i = 0; i < count; i++) 
            { 
                if (String.Compare(infos[i].UIDL, uidl, false) == 0) 
                    return true; 
            } 
            return false; 
        } 

        // Remove the local uidl which is not existed on the server.
        private void _SyncUIDL(MailServer oServer, MailInfo[] infos) 
        { 
            string s = String.Format("{0}#{1} ", oServer.Server, oServer.User); 

            bool bcontinue = false; 
            int n = 0; 
            do 
            { 
                bcontinue = false; 
                int count = m_arUidl.Count; 
                for (int i = n; i < count; i++) 
                { 
                    string x = m_arUidl[i] as string; 
                    if (String.Compare(s, 0, x, 0, s.Length, true) == 0) 
                    { 
                        int pos = x.LastIndexOf(' '); 
                        if (pos != -1) 
                        { 
                            string uidl = x.Substring(pos + 1); 
                            if (!_FindUIDL(infos, uidl)) 
                            { 
                                // This uidl doesn't exist on server,
                                // remove it from local uidl list to save the storage.
                                bcontinue = true; 
                                n = i; 
                                m_arUidl.RemoveAt(i); 
                                break; 
                            } 
                        } 
                    } 
                } 
            } while (bcontinue); 

        } 

        private bool _FindExistedUIDL(MailServer oServer, string uidl) 
        { 
            string s = String.Format("{0}#{1} {2}", oServer.Server.ToLower(), 
                    oServer.User.ToLower(), uidl); 
            int count = m_arUidl.Count; 
            for (int i = 0; i < count; i++) 
            { 
                string x = m_arUidl[i] as string; 
                if (String.Compare(s, x, false) == 0) 
                    return true; 
            } 
            return false; 
        } 

        private void _AddUIDL(MailServer oServer, string uidl) 
        { 
            string s = String.Format("{0}#{1} {2}", oServer.Server.ToLower(), 
                    oServer.User.ToLower(), uidl); 
            m_arUidl.Add(s); 
        } 

        private void _UpdateUIDL() 
        { 
            StringBuilder s = new StringBuilder(); 
            int count = m_arUidl.Count; 
            for (int i = 0; i < count; i++) 
            { 
                s.Append(m_arUidl[i] as string); 
                s.Append("\r\n"); 
            } 

            string file = String.Format("{0}\\{1}", m_curpath, m_uidlfile); 

            FileStream fs = null; 
            try 
            { 
                fs = new FileStream(file, FileMode.Create, FileAccess.Write, FileShare.None); 
                byte[] data = System.Text.Encoding.Default.GetBytes(s.ToString()); 
                fs.Write(data, 0, data.Length); 
                fs.Close(); 
            } 
            catch (Exception ep) 
            { 
                if (fs != null) 
                    fs.Close(); 

                throw ep; 
            } 

        } 

        private void _LoadUIDL() 
        { 
            m_arUidl.Clear(); 
            string file = String.Format("{0}\\{1}", m_curpath, m_uidlfile); 
            StreamReader read = null; 
            try 
            { 
                read = File.OpenText(file); 
                while (true) 
                { 
                    string line = read.ReadLine().Trim("\r\n \t".ToCharArray()); 
                    m_arUidl.Add(line); 
                } 
            } 
            catch (Exception ep) 
            { } 

            if (read != null) 
                read.Close(); 
        } 
        #endregion 

        public void ReceiveEmail(MailServer oServer, bool bLeaveCopy ) 
        { 
            MailClient oClient = new MailClient("TryIt"); 
            m_curpath = Directory.GetCurrentDirectory(); 
            try 
            { 

               // Uidl is the identifier of every email on POP3/IMAP4 server, to
               // avoid retrieve the same email from server more than once,
               // we record the email uidl retrieved every time if you delete the
               // email from server every time and not to leave a copy of email on
               // the server, then please remove all the function about uidl.
                _LoadUIDL(); 

                string mailFolder = String.Format("{0}\\inbox", m_curpath); 
                if (!Directory.Exists(mailFolder)) 
                    Directory.CreateDirectory(mailFolder); 

                Console.WriteLine("Connecting server ... "); 
                oClient.Connect(oServer); 
                MailInfo[] infos = oClient.GetMailInfos(); 
                Console.WriteLine( "Total {0} email(s)", infos.Length); 

                _SyncUIDL(oServer, infos); 
                int count = infos.Length; 

                for (int i = 0; i < count; i++) 
                { 
                    MailInfo info = infos[i]; 
                    if (_FindExistedUIDL(oServer, info.UIDL)) 
                    { 

                        // This email has existed on local disk.
                        continue; 
                    } 

                    Console.WriteLine("Retrieving {0}/{1}...", info.Index, count); 

                    Mail oMail = oClient.GetMail(info); 
                    System.DateTime d = System.DateTime.Now; 
                    System.Globalization.CultureInfo cur = 
                            new System.Globalization.CultureInfo("en-US"); 
                    string sdate = d.ToString("yyyyMMddHHmmss", cur); 
                    string fileName = String.Format("{0}\\{1}{2}{3}.eml", 
                            mailFolder, sdate, d.Millisecond.ToString("d3"), i); 
                    oMail.SaveAs(fileName, true); 

                    if (bLeaveCopy) 
                    { 

                        // Add the email uidl to uidl file to avoid we retrieve it next time.
                        _AddUIDL(oServer, info.UIDL); 
                    } 
                } 

                if (!bLeaveCopy) 
                { 
                    Console.WriteLine( "Deleting ..." ); 
                    for (int i = 0; i < count; i++) 
                        oClient.Delete(infos[i]); 
                } 

                Console.WriteLine("Completed"); 
                // Delete method just mark the email as deleted,
                // Quit method pure the emails from server exactly.
                oClient.Quit(); 

            } 
            catch (Exception ep) 
            { 
                Console.WriteLine(ep.Message); 
            } 

            // Update the uidl list to a text file and then we can load it next time.
            _UpdateUIDL(); 
        } 
    } 
    class Program 
    { 
        static void Main(string[] args) 
        { 
            MailServer oServer = new MailServer("pop3.emailarchitect.net", 
                        "test@emailarchitect.net", "testpassword", ServerProtocol.Pop3 ); 


            MyMailClient oMyClient = new MyMailClient(); 
            // Leave a copy of email on server
            oMyClient.ReceiveEmail(oServer, true); 
        } 
    } 
} 

Click here to read original topic - full version ...

If you have any comments or questions about above example codes, please add your comments here.
thanks 1 user thanked ivan for this useful post.
gpaprinceantony on 5/11/2021(UTC)
gpaprinceantony  
#2 Posted : Tuesday, May 11, 2021 9:53:15 AM(UTC)
gpaprinceantony

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Joined: 5/11/2021(UTC)
Posts: 1
India
Location: Tamil Nadu

Thanks: 1 times
Subject: ddd (Trial Version)

Completed!

I m getting this response. What is the meaning of Trail version.

How the dll fetching only new mails, Is it storing the gmail UID value in some cloud Database.
ivan  
#3 Posted : Tuesday, May 11, 2021 4:15:28 PM(UTC)
ivan

Rank: Administration

Groups: Administrators
Joined: 11/11/2010(UTC)
Posts: 1,102

Thanks: 9 times
Was thanked: 48 time(s) in 48 post(s)
Originally Posted by: gpaprinceantony Go to Quoted Post
Subject: ddd (Trial Version)

Completed!

I m getting this response. What is the meaning of Trail version.

How the dll fetching only new mails, Is it storing the gmail UID value in some cloud Database.


Trial version means you're using a trial version, it will expire after 30 days.

Retrieve new emails only and mark the email as read, but you should use IMAP protocol instead of Pop
https://www.emailarchite...on-imap4-exchange-server
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