.NET使用MailKit进行邮件处理

0.介绍

MimeKit and MailKit are popular fully-featured email frameworks for .NET
框架支持版本如下
Supports .NET 4.5, .NET 4.6, .NET 4.7, .NET 4.8, .NET 5.0, .NETStandard 2.0, Xamarin.Android, Xamarin.iOS, Windows Phone 8.1, and more.

MailKit是最流行且最强大的.NET邮件处理框架之一，下面为大家简单介绍MailKit的使用方式（IMAP为例）

1. 参考资料

Github https://github.com/jstedfast/MailKit
官方Doc http://www.mimekit.net/docs/html/Introduction.htm

2.核心内容（IMAP为例）

• 连接邮箱

加密

client.Connect("imap.exmail.qq.com", 993, SecureSocketOptions.SslOnConnect);

不加密

client.Connect("imap.exmail.qq.com", 143, SecureSocketOptions.None);

• 登入邮箱

client.Authenticate(MAIL_NAME, MAIL_PASSWORD);

• 打开邮件文件夹

client.Inbox.Open(FolderAccess.ReadWrite);

• 读取文件

读取方式一：可以预先筛选邮件

   search for messages where the Subject header contains either "MimeKit" or "MailKit"
   var query = SearchQuery.SubjectContains("MimeKit").Or(SearchQuery.SubjectContains("MailKit"));
   var uids = client.Inbox.Search(query);

读取方式二：读取所有邮件

   var uids = client.Inbox.Search(SearchQuery.All); 

• 邮件操作

操作邮件一：读取邮件标题

    string subject = message.Subject;
    if (!subject.Contains("MimeKitDemo"))
        return;

操作邮件二：读取正文

   string body = message.TextBody ?? string.Empty;
   if (!body.Contains("MimeKitDemoBody"))
       return;

操作邮件三：下载邮件附件

    var attachments = message.Attachments;
    if (attachments.Any())
    {
        foreach (var attachment in attachments)
            DownloadAttachment(attachment);
    }

    private static void DownloadAttachment(MimeEntity attachment)
    {
        if (attachment is MessagePart)
        {
            var fileName = attachment.ContentDisposition?.FileName;
            var rfc822 = (MessagePart)attachment;

            if (string.IsNullOrEmpty(fileName))
                fileName = "attached-message.eml";

            var path = Path.Combine(DIRECTORY, fileName);
            using (var stream = File.Create(path))
                rfc822.Message.WriteTo(stream);
        }
        else
        {
            var part = (MimePart)attachment;
            var fileName = part.FileName;

            var path = Path.Combine(DIRECTORY, fileName);
            using (var stream = File.Create(path))
                part.Content.DecodeTo(stream);
        }
    }
    

操作邮件四：移动邮件（移动至删除文件夹）

 
    client.Inbox.MoveTo(uid, client.GetFolder(SpecialFolder.Trash));

操作邮件五：删除邮件 – 将邮件标记为删除、最后删除

    client.Inbox.AddFlags(uid, MessageFlags.Deleted, true);
    client.Inbox.Expunge();

3.样例源码地址

https://github.com/Impartsoft/Bins/tree/main/MailKitDemo