您是否有机会连接到GMail?

Are you connecting to GMail, by any chance?

这是GMail行为，根据您的POP设置(在GMail网络应用的设置"页面中进行设置)，它将确定客户端看到的消息.

This is a GMail behavior where, depending on your POP settings (as set in the GMail web app Settings page), will determine what messages the client sees.

这不是MailKit问题.

This is not a MailKit issue.

来自Google自己的常见问题解答在电子邮件下载不正确"，其中指出:

From Google's own FAQ in the section titled "Emails aren't downloading correctly", it states:

在Gmail设置中设置POP后，您的电子邮件将可用 分批.可能需要一段时间才能看到您的所有电子邮件.

After you set up POP in your Gmail settings, your emails become available in batches. It might take a while to see all your emails.

注意:Gmail会下载您发送或接收的每封电子邮件的副本，但 用于聊天"，垃圾邮件"和已删除邮件"中的电子邮件.为避免重复，Gmail不会 下载在您的邮件客户端中发送的电子邮件，但是您仍然可以看到它们 如果您登录到Gmail.

Note: Gmail downloads a copy of every email you send or receive, except for emails in Chats, Spam, and Trash. To avoid duplicates, Gmail doesn't download emails sent within your mail client, but you can still see them if you log in to Gmail.

如果您仍然无法下载电子邮件，请尝试使用最新的 模式:

If you continue to have problems downloading emails, try using recent mode:

1. 在电子邮件客户端的POP设置页面中，找到电子邮件地址"或 用户名"字段.
2. 添加最新消息:在您的电子邮件地址之前.例如， 最近:example@gmail.com.

1. In your email client's POP settings page, find the "Email address" or "User name" field.
2. Add recent: in front of your email address. For example, recent:example@gmail.com.

如果仍不能解决问题，请尝试从电子邮件客户端中删除您的Gmail地址，然后重新添加.

If that doesn't fix the problem, try deleting your Gmail address from your email client, then re-adding it.