This makes quite difficult for an IMAP client to know the real purpose of the folders on the server.

Fortunately there are two IMAP protocol extensions:

• XLIST – supported by Gmail
• SPECIAL-USE – RFC 6154 standardized extension

You can check if your servers support it by checking if SupportedExtensions returns ImapExtension.XList or ImapExtension.SpecialUse

Both extensions are supported by Mail.dll and, if your server supports any of them, you can take advantage of CommonFolders class. CommonFolders allows you to get the name of the folder and Select it, by knowing its purpose (for example Spam folder may be called “Junk email” on the server).

// C# version:

using (Imap imap = new Imap())
{
    imap.ConnectSSL("imap.gmail.com");
    imap.UseBestLogin("pat@gmail.com", "password");

    CommonFolders folders = new CommonFolders(imap.GetFolders());

    Console.WriteLine("Inbox folder: " + folders.Inbox.Name);
    Console.WriteLine("Sent folder: " + folders.Sent.Name);
    Console.WriteLine("Spam folder: " + folders.Spam.Name);

    // You can select folders easy:
    imap.Select(folders.Inbox);
    imap.Select(folders.Sent);
    imap.Select(folders.Spam);

    imap.Close();
}

' VB.NET version:

Using imap As New Imap()
    imap.ConnectSSL("imap.gmail.com")
    imap.UseBestLogin("pat@gmail", "password")

    Dim folders As New CommonFolders(imap.GetFolders())

    Console.WriteLine("Inbox folder: " + folders.Inbox.Name)
    Console.WriteLine("Sent folder: " + folders.Sent.Name)

    ' You can select folders easy:
    imap.Select(folders.Inbox)
    imap.Select(folders.Sent)


    imap.Close()
End Using

You can check if you can use CommonFolders with following code:

// C#

List<ImapExtension> extensions = client.SupportedExtensions();
bool canUseCommonFolders = extensions.Contains(ImapExtension.XList) 
    || extensions.Contains(ImapExtension.SpecialUse);

' VB.NET

Dim extensions As List(Of ImapExtension) = client.SupportedExtensions()
Dim canUseCommonFolders As Boolean = extensions.Contains(ImapExtension.XList) OrElse extensions.Contains(ImapExtension.SpecialUse)

The post Common IMAP folders first appeared on Blog | Limilabs.

• Extension of the LIST command: XLIST
• Extension of the SEARCH command: X-GM-RAW
• Access to the Gmail unique message ID: X-GM-MSGID
• Access to the Gmail thread ID: X-GM-THRID
• Access to Gmail labels: X-GM-LABELS
• OAuth and OAuth 2.0: XOAUTH, XOAUTH2

You can read on how to use Mail.dll with Gmail in the following articles:

• Get Gmail thread id
• Search Gmail thread id
• Get Gmail message id
• Search Gmail message id
• Get Gmail labels for specified messages
• Label message with Gmail label
• Search Gmail label
• Localized Gmail IMAP Folders
• Search Gmail using Gmail’s search syntax
• Create Gmail url-ID via IMAP

OAuth 2.0

• OAuth 2.0 with Gmail over IMAP for web applications
• OAuth 2.0 with Gmail over IMAP for installed applications

OAuth 1.0

• OAuth with Gmail
• 2-legged OAuth with Gmail
• Get Google contacts

The post Gmail extensions in Mail.dll first appeared on Blog | Limilabs.

XLIST provides additional folder flags such as Inbox or Spam (which are very useful if folder names are localized to know the purpose of the folder).

Mail.dll automatically uses XLIST if it is supported by the server. You can read more about XLIST here:
/blog/localized-gmail-imap-folders

Unfortunately when you ask for subscribed folders with LSUB command, those additional flags are not send by the server. There is no such thing as XLSUB command.

The only way to workaround this limitation is to first download all folders with flags using XLIST, then use LSUB to get subscribed folders and finally match the flags by name.

The post IMAP: LIST, XLIST and LSUB first appeared on Blog | Limilabs.

There are no well-know names for common folders such as Drafts, Trash, Spam, … on IMAP servers.

The problem is even worse when you use localized version of IMAP client. Gmail folder names are localized with respect to the user localization settings, so ‘[Gmail]/All Mail’ show as ‘[Gmail]/Todos’ to Spanish users for example.

Google and Apple developed a special IMAP XLIST command to address this issue.

IMAP XLIST command returns a list of folders and their well-know flags.

Here’s the sample XLIST response:


C: A001 CAPABILITY
S: * CAPABILITY IMAP4rev1 ID XLIST ...
S: A001 OK Thats all she wrote! 17if1168678ebj.35
C: A002 XLIST "" "*"
S: * XLIST (\HasNoChildren \Inbox) "/" "Inbox"
S: * XLIST (\HasNoChildren \AllMail) "/" "[Gmail]/All Mail"
S: * XLIST (\HasNoChildren \Drafts) "/" "[Gmail]/Drafts"
S: * XLIST (\HasNoChildren \Spam) "/" "[Gmail]/Spam"
...


As you can see XLIST is advertised in CAPABILITY response.
You can probably spot additional flags in the XLIST response: \AllMail, \Spam, \Drafts…

Mail.dll IMAP library supports XLIST command (and SPECIAL-USE extension). It is used automatically when server advertises support for this feature.

You can use CommonFolders class to match folder names with they real purpose.

Take a look at the examples:

// C# version:

using (Imap imap = new Imap())
{
    imap.ConnectSSL("imap.gmail.com");
    imap.UseBestLogin("pat@gmail.com", "app-password");

    CommonFolders folders = new CommonFolders(imap.GetFolders());

    Console.WriteLine("Inbox folder: " + folders.Inbox.Name);
    Console.WriteLine("Sent folder: " + folders.Sent.Name);

    // You can select folders easy:

    imap.Select(folders.Inbox);
    imap.Select(folders.Sent);

    imap.Close();
}

' VB.NET version:

Using imap As New Imap()
    imap.ConnectSSL("imap.gmail.com")
    imap.UseBestLogin("pat@gmail", "app-password")

    Dim folders As New CommonFolders(imap.GetFolders())

    Console.WriteLine("Inbox folder: " + folders.Inbox.Name)
    Console.WriteLine("Sent folder: " + folders.Sent.Name)

    ' You can select folders easy:

    imap.Select(folders.Inbox)
    imap.Select(folders.Sent)

    imap.Close()
End Using

Remember to enable IMAP in Gmail (your authentication options are app-passwords and OAuth 2.0).

The post Localized Gmail IMAP folders first appeared on Blog | Limilabs.