我在设置电子邮件的过期时间时遇到问题。
我使用System.Net.Mail.MailMessage但我没有找到任何可以处理这个问题的属性。我在 Outlook 中看到这是可能的。我在 StackOverflow、MSDN 和 Google 上进行了一些搜索，但找不到适合我需要的答案。
这就是它在 Outlook 中的设置方式http://blogs.mccombs.utexas.edu/the-most/2011/02/24/set-outlook-emails-to-delete-in-the-future/
问题是如何使用 C#在MailMessage上设置 Expires After。是否需要设置任何标题或是否有任何其他方法可以做到这一点？这可能吗？
据我所知，我们的 Exchange 服务器会处理收到的邮件过期。因此，从您的角度来看，这不是您可以放在邮件标头中的任何内容，而是由客户电子邮件帐户提供商处理的。
另一方面：EmailMessageClass具有您正在寻找的属性。
/edit：如果您发送的电子邮件包含一个链接，该链接会将用户重定向回您的页面，您可以检查您的数据库是否电子邮件有效（过期）每次发送电子邮件时，保存时间戳和您的用户已将电子邮件发送至。如果用户通过您邮件提供的链接返回，您可以检查实际时间是否在到期日期之前。（例如 DateSend + 2 周）
mail.Headers.Add("expiry-date", sTime);
例如
namespace RedmineMailService
{
// https://stackoverflow.com/questions/637866/sending-mail-without-installing-an-smtp-server
// http://www.nullskull.com/articles/20030316.asp
// https://www.redmine.org/boards/2/topics/26198
// https://www.redmine.org/boards/2/topics/22259
static class MailSender
{
public static void Test()
{
using (System.Net.Mail.SmtpClient client = new System.Net.Mail.SmtpClient())
{
using (System.Net.Mail.MailMessage mail = new System.Net.Mail.MailMessage())
{
client.Port = 25;
client.DeliveryMethod = System.Net.Mail.SmtpDeliveryMethod.Network;
client.UseDefaultCredentials = false;
// client.UseDefaultCredentials = true;
// Must be after UseDefaultCredentials
// client.Credentials = new System.Net.NetworkCredential("mailboxname", "password", "example.com");
// client.Port = 587;
// client.EnableSsl = true;
client.Host = "COR-EXCHANGE.cor.local";
mail.Subject = "this is a test email.";
mail.Body = "Test";
// https://www.iana.org/assignments/message-headers/message-headers.xhtml
// https://tools.ietf.org/html/rfc4021#page-32
// mail.Headers.Add("Importance", "High"); // High, normal, or low.
mail.Priority = System.Net.Mail.MailPriority.High;
// for read-receipt
mail.Headers.Add("Disposition-Notification-To", RedmineMailService.Trash.UserData.info);
string sTime = System.DateTime.UtcNow.AddDays(-1).ToString("dd MMM yyyy", System.Globalization.CultureInfo.InvariantCulture) + " " +
System.DateTime.UtcNow.ToShortTimeString() + " +0000"; // Fixed, from +0100 - just take UTC - works in .NET 2.0 - no need for offset
// Set a message expiration date
// When the expiration date passes, the message remains visible
// in the message list with a strikethrough.
// It can still be opened, but the strikethrough gives a visual clue
// that the message is out of date or no longer relevant.
mail.Headers.Add("expiry-date", sTime);
// https://tools.ietf.org/html/rfc2076#page-16
// https://tools.ietf.org/html/rfc1911
// The case-insensitive values are "Personal" and "Private"
// Normal, Confidential,
// If a sensitivity header is present in the message, a conformant
// system MUST prohibit the recipient from forwarding this message to
// any other user. If the receiving system does not support privacy and
// the sensitivity is one of "Personal" or "Private", the message MUST
// be returned to the sender with an appropriate error code indicating
// that privacy could not be assured and that the message was not
// delivered [X400].
mail.Headers.Add("Sensitivity", "Company-confidential");
// for delivery receipt
mail.DeliveryNotificationOptions =
System.Net.Mail.DeliveryNotificationOptions.OnSuccess
| System.Net.Mail.DeliveryNotificationOptions.OnFailure;
// mail.From = new System.Net.Mail.MailAddress("somebody@friends.com", "SomeBody");
mail.From = new System.Net.Mail.MailAddress(RedmineMailService.Trash.UserData.info, "COR ServiceDesk");
mail.To.Add(new System.Net.Mail.MailAddress(RedmineMailService.Trash.UserData.Email, "A"));
// mail.To.Add(new System.Net.Mail.MailAddress("user1@friends.com", "B"));
// mail.To.Add(new System.Net.Mail.MailAddress("user2@friends.com", "B"));
// mail.To.Add(new System.Net.Mail.MailAddress(RedmineMailService.Trash.UserData.info, "ServiceDesk"));
try
{
System.Console.WriteLine("Host: " + client.Host);
System.Console.WriteLine("Credentials: " + System.Convert.ToString(client.Credentials));
client.Send(mail);
System.Console.WriteLine("Mail versendet");
}
catch (System.Exception ex)
{
do
{
System.Console.Write("Fehler: ");
System.Console.WriteLine(ex.Message);
System.Console.WriteLine("Stacktrace: ");
System.Console.WriteLine(ex.StackTrace);
System.Console.WriteLine(System.Environment.NewLine);
ex = ex.InnerException;
} while (ex != null);
} // End Catch
} // End Using mail
} // End Using client
} // End Sub Test
} // End Class MailSender
} // End Namespace RedmineMailService.Trash