public bool IsZip { get; }

Public ReadOnly Property IsZip As Boolean
	Get

// To use the code below, import MailBee namespaces at the top of your code.
using MailBee;
using MailBee.Mime;

// The actual code (put it into a method of your class)

// Load the message from file.
MailMessage msg = new MailMessage();
msg.LoadMessage(@"C:\Docs\TestMail.eml");

// For every attachment...
foreach (Attachment attach in msg.Attachments)
{
    // ...when the attachment is a zip file...
    if (attach.IsZip)
    {
        // ...show its filename.
        Console.WriteLine("Attachment " + attach.Filename + " is a zip archive.");
    }
}

' To use the code below, import MailBee namespaces at the top of your code.
Imports MailBee
Imports MailBee.Mime

' The actual code (put it into a method of your class)

' Load the message from file.
Dim msg As New MailMessage
msg.LoadMessage("C:\Docs\TestMail.eml")

' For every attachment...
For Each attach As Attachment In msg.Attachments
    ' ...when the attachment is a zip file...
    If attach.IsZip Then
        ' ...show its filename.
        Console.WriteLine("Attachment " & attach.Filename & " is zip archive.")
    End If
Next