Azure 应用服务：SMTP 异常系统存储不足

问题描述

我们有一个 azure 应用服务，突然间我们看到了这个错误：

System.Net.Mail.SmtpException: Insufficient system storage. The server response was: 4.3.1 Out of memory at System.Net.Mail.SendMailAsyncResult.End(IAsyncResult result) at System.Net.Mail.SmtpClient.SendMailCallback(IAsyncResult result) --- End of stack trace from prevIoUs location where exception was thrown --- at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task) at

我们已经向发送电子邮件的提供商发出了一张票，但他们说他们没有发现问题。现在我们认为我们在上一个版本中推送了一些可能导致问题的内容。当然，我们目前还没有发现任何东西。

只是好奇其他人是否有这些问题以及最终结果是什么？

我们也在 Azure 中的其他应用服务上使用了此代码，但这些服务由不同的客户（不同的实例）控制。现在有问题的是一个新客户，我们在一周前的星期一推送了我们的代码。不过上周似乎一切都很好。

这是我们的 SMTP 代码：

/// <summary>
/// Send an email via code. All email's with attachments are sent through code.
/// </summary>
/// <param name="email">Email Data</param>
/// <param name="smtpServer">The SMTP server.</param>
/// <returns>
/// Task
/// </returns>
private async Task SendSMTPEmail(EmailDTO email,SMTPServerDTO smtpServer)
{
    SmtpClient smtp = null;

    if (email == null)
    {
        throw new ArgumentNullException(nameof(email));
    }

    if (smtpServer == null)
    {
        throw new ArgumentNullException(nameof(smtpServer));
    }

    if (!smtpServer.Port.HasValue)
    {
        smtp = new SmtpClient(smtpServer.HostName);
    }
    else
    {
        smtp = new SmtpClient(smtpServer.HostName,smtpServer.Port.Value);
    }

    // Sets the NetworkCredential if a user name and password is required
    if (!string.IsNullOrWhiteSpace(smtpServer.Username) && !string.IsNullOrWhiteSpace(smtpServer.Password))
    {
        smtp.Credentials = new System.Net.NetworkCredential(smtpServer.Username,smtpServer.Password);
    }

    MailMessage mailMessage = new MailMessage
    {
        From = new MailAddress(email.FromAddress)
    };

    foreach (string toAddress in email.ToAddresses)
    {
        mailMessage.To.Add(new MailAddress(toAddress));
    }

    foreach (string ccAddress in email.CCAddresses)
    {
        mailMessage.CC.Add(ccAddress);
    }

    foreach (string bccAddress in email.BCCAddresses)
    {
        mailMessage.Bcc.Add(bccAddress);
    }

    if (!string.IsNullOrWhiteSpace(email.ReplyToAddress))
    {
        mailMessage.ReplyToList.Add(email.ReplyToAddress);
    }

    mailMessage.Subject = email.Subject;

    mailMessage.Body = email.Body;

    if (!string.IsNullOrWhiteSpace(email.Importance))
    {
        email.Importance = email.Importance.ToLower();
    }

    switch (email.Importance)
    {
        case "low":
            mailMessage.Priority = MailPriority.Low;
            break;
        case "normal":
            mailMessage.Priority = MailPriority.normal;
            break;
        case "high":
            mailMessage.Priority = MailPriority.High;
            break;
        default:
            mailMessage.Priority = MailPriority.normal;
            break;
    }

    if (!string.IsNullOrWhiteSpace(email.Sensitivity))
    {
        mailMessage.Headers.Add("Sensitivity",email.Sensitivity);
    }
    else
    {
        mailMessage.Headers.Add("Sensitivity",EmailSensitivityConstants.CompanyConfidential);
    }

    foreach (EmailAttachmentDTO emailAttachment in email.Attachments)
    {
        byte[] attachmentData = Convert.FromBase64String(emailAttachment.FileData);
        MemoryStream memoryStream = new MemoryStream(attachmentData);

        System.Net.Mail.Attachment attachment = new System.Net.Mail.Attachment(memoryStream,emailAttachment.FileName);

        mailMessage.Attachments.Add(attachment);
    }

    await smtp.SendMailAsync(mailMessage).ConfigureAwait(false);
}

解决方法

问题出在我们 Azure 实例中电子邮件服务的第 3 方提供商。这导致我们的应用服务等出现内存不足问题。

从未听到他们为解决问题所做的工作。

电子邮件现在可以正常发送。

azure-web-app-service smtpclient