尝试使用VB.net读取第一封电子邮件

Imports System.Net
Imports System.Net.Mail

Module Module1
    Sub Main()
        ' 邮箱服务器地址和端口
        Dim server As String = "邮件服务器地址"
        Dim port As Integer = 993

        ' 邮箱账号和密码
        Dim username As String = "邮箱账号"
        Dim password As String = "邮箱密码"

        ' 创建一个IMAP客户端对象
        Dim client As New ImapClient(server, port, username, password)

        ' 连接到服务器
        client.Connect()

        ' 选择收件箱
        client.SelectMailbox("INBOX")

        ' 获取收件箱中的邮件列表
        Dim messages As List(Of MailMessage) = client.GetMessages()

        ' 判断是否有邮件
        If messages.Count > 0 Then
            ' 获取第一封邮件
            Dim firstMessage As MailMessage = messages(0)

            ' 打印邮件信息
            Console.WriteLine("发件人: " & firstMessage.From.Address)
            Console.WriteLine("主题: " & firstMessage.Subject)
            Console.WriteLine("正文: " & firstMessage.Body)
        Else
            Console.WriteLine("收件箱中没有邮件。")
        End If

        ' 断开连接
        client.Disconnect()

        Console.ReadLine()
    End Sub
End Module

' 自定义IMAP客户端类
Public Class ImapClient
    Private server As String
    Private port As Integer
    Private username As String
    Private password As String
    Private client As Net.Sockets.TcpClient
    Private stream As Net.Security.SslStream

    Public Sub New(server As String, port As Integer, username As String, password As String)
        Me.server = server
        Me.port = port
        Me.username = username
        Me.password = password
    End Sub

    Public Sub Connect()
        ' 创建TCP客户端对象
        client = New Net.Sockets.TcpClient(server, port)

        ' 创建SSL流对象
        stream = New Net.Security.SslStream(client.GetStream())

        ' 进行SSL握手
        stream.AuthenticateAsClient(server)

        ' 发送登录命令
        SendCommand("LOGIN " & username & " " & password)
    End Sub

    Public Sub Disconnect()
        ' 发送退出命令
        SendCommand("LOGOUT")

        ' 关闭流和客户端
        stream.Close()
        client.Close()
    End Sub

    Public Sub SelectMailbox(mailbox As String)
        ' 发送选择邮箱命令
        SendCommand("SELECT " & mailbox)
    End Sub

    Public Function GetMessages() As List(Of MailMessage)
        Dim messages As New List(Of MailMessage)

        ' 发送搜索命令
        SendCommand("SEARCH ALL")

        ' 获取搜索结果
        Dim response As String = ReadResponse()

        ' 解析搜索结果
        Dim messageIds As String() = response.Split(" "c)
        For Each messageId As String In messageIds
            If messageId <> "" Then
                ' 发送获取邮件命令
                SendCommand("FETCH " & messageId & " (BODY.PEEK[])")

                ' 获取邮件内容
                Dim messageContent As String = ReadResponse()

                ' 解析邮件内容
                Dim message As MailMessage = ParseMessage(messageContent)
                messages.Add(message)
            End If
        Next

        Return messages
    End Function

    Private Sub SendCommand(command As String)
        ' 将命令转换为字节数组
        Dim commandBytes As Byte() = System.Text.Encoding.ASCII.GetBytes(command & vbCrLf)

        ' 发送命令
        stream.Write(commandBytes, 0, commandBytes.Length)
    End Sub

    Private Function ReadResponse() As String
        ' 读取服务器响应
        Dim responseBytes(8191) As Byte
        Dim bytesRead As Integer = stream.Read(responseBytes, 0, responseBytes.Length)

        ' 将响应转换为字符串
        Dim response As String = System.Text.Encoding.ASCII.GetString(responseBytes, 0, bytesRead)

        Return response
    End Function

    Private Function ParseMessage(content As String) As MailMessage
        ' 解析邮件内容并创建MailMessage对象
        Dim message As New MailMessage()

        ' 解析发件人
        Dim fromIndex As Integer = content.IndexOf("From: ") + 6
        Dim toIndex As Integer = content.IndexOf(vbCrLf, fromIndex)
        Dim fromAddress As String = content.Substring(fromIndex, toIndex - fromIndex)
        message.From = New MailAddress(fromAddress)

        ' 解析主题
        Dim subjectIndex As Integer = content.IndexOf("Subject: ") + 9
        Dim subjectEndIndex As Integer = content.IndexOf(vbCrLf, subjectIndex)
        Dim subject As String = content.Substring(subjectIndex, subjectEndIndex - subjectIndex)
        message.Subject = subject

        ' 解析正文
        Dim bodyIndex As Integer = content.IndexOf(vbCrLf & vbCrLf) + 4
        Dim body As String = content.Substring(bodyIndex)
        message.Body = body

        Return message
    End Function
End Class