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ivan  
#1 Posted : Monday, April 11, 2011 4:59:12 AM(UTC)
ivan

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C++/CLI 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 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

Code:

#include "stdafx.h" 

using namespace System; 
using namespace System::Text; 
using namespace System::Collections; 
using namespace System::IO; 

// Add EAGetMail namespace
using namespace EAGetMail; 

public ref class MyMailClient 
{ 
private: String ^m_uidlfile; 
private: String ^m_curpath; 
private: ArrayList ^m_arUidl; 
// 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( array<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, array<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 = dynamic_cast<String^>( m_arUidl[i]); 
            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,
                        // so we should remove it from local uidl list.
                        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 = dynamic_cast<String^>(m_arUidl[i]); 
        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 = gcnew StringBuilder(); 
    int count = m_arUidl->Count; 
    for( int i = 0; i < count; i++ ) 
    { 
        s->Append( dynamic_cast<String^>(m_arUidl[i])); 
        s->Append( "\r\n" ); 
    } 

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

    FileStream ^fs = nullptr; 
    try 
    { 
        fs = gcnew FileStream( file, FileMode::Create, FileAccess::Write, FileShare::None ); 
        array<unsigned char>^ data = System::Text::Encoding::Default->GetBytes( s->ToString()); 
        fs->Write( data, 0, data->Length ); 
        fs->Close(); 
    } 
    catch(Exception ^ep ) 
    { 
        if( fs != nullptr ) 
            fs->Close(); 

        throw ep; 
    } 

} 

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

    if( read != nullptr ) 
        read->Close(); 
} 

public: void ReceiveEmail(MailServer ^oServer, bool bLeaveCopy ) 
{ 
    m_arUidl = gcnew ArrayList(); 
    m_uidlfile = "uidl.txt"; 
    MailClient ^oClient = gcnew 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); 
        array<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 = 
                gcnew 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(); 
} 

}; 

int main(array<System::String ^> ^args) 
{ 
    // Create a folder named "inbox" under current directory
    // to save the email retrieved.
    String ^curpath = Directory::GetCurrentDirectory(); 
    String ^mailbox = String::Format("{0}\\inbox", curpath); 

    // If the folder is not existed, create it.
    if (!Directory::Exists(mailbox)) 
    { 
        Directory::CreateDirectory(mailbox); 
    } 

    MailServer ^oServer = gcnew MailServer("pop3.emailarchitect.net", 
        "test@emailarchitect.net", "testpassword", ServerProtocol::Pop3 ); 
    MailClient ^oClient = gcnew MailClient("TryIt"); 

    // If your POP3 server requires SSL connection,
    // Please add the following codes:
    // oServer->SSLConnection = true;
    // oServer->Port = 995;

    MyMailClient ^MyClient = gcnew MyMailClient(); 
    MyClient->ReceiveEmail( oServer, true ); 

    return 0; 
} 

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