无法从Azure云服务连接到SMTP [英] Not able to connect to smtp from Azure Cloud Service

问题描述

我们在Azure上托管了2个云服务.

这两种服务都依赖于我们的smtp服务器发送邮件.

问题是Azure云服务无法连接到我们的smtp服务器.

我们能够在内部计算机上使用相同的代码，而不会出现任何问题.我们还检查了25个端口是否已打开，并且IP地址也未列入黑名单.

以下是从云服务进行连接时的错误:

连接尝试失败，因为被连接方未一段时间后正确响应或建立连接失败，因为连接的主机未能响应111.93.111.42:25

电子邮件发送逻辑

  MailMessage消息=新的MailMessage(senderID，提醒.用户名，template.Subject，正文);message.From =新MailAddress(data.SenderEmail，data.SenderName);message.IsBodyHtml = true;尝试{SmtpClient smtp =新的SmtpClient{主机= data.SMTPServer，//此处的smtp服务器地址...端口=数据.端口号，EnableSsl = data.SSL，DeliveryMethod = SmtpDeliveryMethod.Network，凭据=新的System.Net.NetworkCredential(senderID，senderPassword)，超时= 30000，};smtp.Send(消息);//线程=新线程(()=> {smtp.Send(message);});//th.Start();}抓住(前例外){ErrorLogging.ErrorLog(例如，错误提醒发送邮件-员工提醒邮件错误消息:" + ex.Message，员工提醒邮件"，"0"，"EmployeeRemindersMail"，schemaName，companyId)；} 

解决方案

Microsoft建议Azure客户使用经过身份验证的SMTP中继服务(通常通过TCP端口587或443连接，但通常也支持其他端口)来发送电子邮件.Azure VM或来自Azure App Services.这些服务专门研究发件人的信誉，以最大程度地降低第三方电子邮件提供商拒绝邮件的可能性.此类SMTP中继服务包括但不限于 SendGrid .也可以在可以使用的前提下运行安全的SMTP中继服务.无论订阅类型如何，在Azure中都不会限制使用这些电子邮件传递服务.

参考: https://blogs.msdn.microsoft.com/mast/2017/11/15/enhanced-azure-security-for-sending-emails-november-2017-update/

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解决方案

Microsoft recommends that Azure customers employ authenticated SMTP relay services (typically connected via TCP port 587 or 443, but often support other ports too) to send e-mail from Azure VMs or from Azure App Services. These services specialize in sender reputation to minimize the possibility 3rd party e-mail providers will reject the message. Such SMTP relay services include but are not limited to SendGrid. It is also possible you have a secure SMTP relay service running on premises that can be used. Use of these e-mail delivery services is in no way restricted in Azure regardless of subscription type.

Reference: https://blogs.msdn.microsoft.com/mast/2017/11/15/enhanced-azure-security-for-sending-emails-november-2017-update/

You may also want to refer this thread which addresses similar issue and see if that helps.

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