Sends log messages by email using SMTP protocol.

Platforms Supported: All - Requires nuget-package NLog.Targets.Mail since NLog v6, or alternative MailKit

• Can also be combined with FallbackGroup to fallback to alternative SMTP-server on error. See example here.
• Can also be combined with BufferingWrapper to group multiple logevents into a single email.
• Can also be combined with LimitingWrapper to throttle the number of emails.
• Can also be combined with FilteringWrapper to avoid repeating identical emails.

<targets>
  <target xsi:type="Mail"
          name="String"
          header="Layout"
          footer="Layout"
          layout="Layout"
          html="Boolean"
          addNewLines="Boolean"
          replaceNewlineWithBrTagInHtml="Boolean"
          encoding="Encoding"
          subject="Layout"
          to="Layout"
          bcc="Layout"
          cc="Layout"
          from="Layout"
          body="Layout"
          smtpUserName="Layout"
          enableSsl="Boolean"
          secureSocketOption="None|Auto|SslOnConnect|StartTls|StartTlsWhenAvailable"*
          smtpPassword="Layout"
          smtpAuthentication="Enum"
          smtpServer="Layout"
          smtpPort="Integer"
          useSystemNetMailSettings="Boolean"
          deliveryMethod="Enum"
          pickupDirectoryLocation="String"
          timeout="Integer"
          skipCertificateValidation="Boolean"
          priority="Layout">
     <mailheader name="header-name" layout="header-value" /> <!-- repeatable -->
 </target>
</targets>

Read more about using the Configuration File.

• name - Name of the target.

• header - Header for the message-body. Layout

• footer - Footer for the message-body. Layout

• layout - Text to be rendered for message-body. Layout Required. Default: ${message}${newline}.

• html - Indicates whether to send message as HTML instead of plain text. Boolean Default: false

• addNewLines - Indicates whether to add new lines between log entries. Boolean

• replaceNewlineWithBrTagInHtml - Indicates whether NewLine characters in the body should be replaced with <br/> tags. Boolean Default: false

• encoding - Encoding to be used for sending e-mail. Encoding Default: UTF-8

• subject - Mail subject. Layout Required. Default: Message from NLog on ${machinename}

• to - Recipients' email addresses separated by semicolons (e.g. john@domain.com;jane@domain.com). Layout.

• bcc - BCC email addresses separated by semicolons (e.g. john@domain.com;jane@domain.com). Layout

• cc - CC email addresses separated by semicolons (e.g. john@domain.com;jane@domain.com). Layout

• from - Sender's email address (e.g. joe@domain.com). Layout Required.

• body - Same as Layout property. Mail message body (repeated for each log message send in one mail). Layout Default: ${message}${newline}

• priority - The mail message priority. Low / Normal / High

  • NLog.MailKit v3.2 (and newer) accepts NonUrgent / Low , Normal , Urgent / High (Supports MimeKit.MessagePriority)

• smtpServer - SMTP Server to be used for sending. Layout Required.

• smtpPort - Port number that SMTP Server is listening on. Integer Default: 25. Note: port 465 isn't working with SSL. See issue 1226

• smtpAuthentication - SMTP Authentication mode. Default: None
  Possible values:

  • Basic - Basic - username and password.
  • None - No authentication.
  • Ntlm - NTLM Authentication using network credentials of user currently logged on (Same as SmtpClient.UseDefaultCredentials = true)
  • OAuth2 - NLog.Mailkit ver. 6.1.3 (and newer) supports OAuth2 authentication where SmtpUserName provides clientid, and SmtpPassword provides clientSecret/accessToken.

• smtpUserName - Username used to connect to SMTP server (used when SmtpAuthentication is set to "basic"). Layout

• smtpPassword - Password used to authenticate against SMTP server (used when SmtpAuthentication is set to "basic"). Layout

• enableSsl - Indicates whether SSL (secure sockets layer) should be used when communicating with SMTP server. Boolean Default: False.

  Notice SMTP/SSL, SMTP over SSL, or SMTPS with port 465 is only supported by NLog.MailKit. See issue 1226

• secureSocketOption - NLog.Mailkit ver. 2.1 (and newer) supports both SSL / TLS encryption. Default: StartTlsWhenAvailable. Possible values:

  • None - No SSL or TLS encryption should be used.
  • Auto - Allow the MailKit.IMailService to decide which SSL or TLS options to use. If the server does not support SSL or TLS, then no encryption.
  • SslOnConnect - The connection should use SSL or TLS encryption immediately.
  • StartTls - The connection should use TLS encryption immediately.
  • StartTlsWhenAvailable - Elevates the connection to use TLS encryption immediately, when supported by server.

• useSystemNetMailSettings - Force using smtp configuration from system.net/mailSettings. Boolean Default: False

• timeout - Indicates the SMTP client timeout in milliseconds. Integer Default: 10000 (10 seconds)

• pickupDirectoryLocation - Gets or sets the folder where applications save mail messages to be processed by the local SMTP server (introduced in NLog 4.2).

• deliveryMethod - Specifies how outgoing email messages will be handled (introduced in NLog 4.2). Default: Network Possible values:

  • Network - Email is sent through the network to an SMTP server.
  • PickupDirectoryFromIis - Email is copied to the pickup directory used by a local Internet Information Services (IIS) for delivery.
  • SpecifiedPickupDirectory - Email is copied to the directory specified by the PickupDirectoryLocation property for delivery by an external application.

• skipCertificateValidation - NLog.Mailkit ver. 1.1 (and newer) can skip SSL certificate validation check. Maybe useful for self-signed certificates, but not recommended for production.

• mailheader - Specify one or more email-message-headers (Ex. Message-Id)

  Introduced with NLog v5.1.3 and NLog.MailKit v5.1

The SmtpClient is not part of .NET Standard 1.x. Also notice that the original SmtpClient of .NET is obsolete in favor of MailKit:

The NLog.MailKit is the Mail target implementation which uses MailKit. Including the NLog.MailKit package will replace the original mail target and has the same options as the original mail target

• Install-Package NLog.MailKit

or use

<PackageReference Include="NLog.MailKit" Version="3.0.0" />

And add to your nlog.config:

<nlog>
  <extensions>
    <add assembly="NLog.MailKit"/>
  </extensions>
  ...

Bug/feature requests for NLog.MailKit please on the NLog.MailKit repo

If the application config file contains mail settings, fx.:

<system.net>
  <mailSettings>
    <smtp from="mail@domain.com" deliveryMethod="SpecifiedPickupDirectory">
      <network host="localhost" port="25"/>
      <specifiedPickupDirectory pickupDirectoryLocation="C:/Temp/Email"/>
    </smtp>
  </mailSettings>
</system.net>

These values will be used, if target doesn't override them (see useSystemNetMailSettings attribute).

• NetStandard2.X does not support mail settings in the application config file.

It is possible to use an address in format "John Doe <john.doe@example.com>" but the special characters < and > must be escaped. The result would be John Doe <john.doe@example.com>

<target name="MailAWS" xsi:type="Mail"
            smtpServer="email-smtp.us-east-1.amazonaws.com"
            smtpPort="587"
            smtpAuthentication="Basic"
            smtpUserName="xxxxxxxx"
            smtpPassword="xxxxxxxxxx"
            secureSocketOption="StartTls"
            from="logger@xxxx.xxx" to="xxx@gmail.com" />

Example configuration for a Mailserver Fallback with multiple hosts.

<target xsi:type="FallbackGroup" 
        name="mail"
        returnToFirstOnSuccess="true">
    <target xsi:type="Mail"
            name="mailserver1"
            subject="Layout"
            to="Layout"
            from="Layout"
            smtpServer="mx1.example.com" 
            smtpPort="Integer"
            layout="Layout" />
    <target xsi:type="Mail"
            name="mailserver2" 
            subject="Layout"
            to="Layout"
            from="Layout"
            smtpServer="mx2.example.com" 
            smtpPort="Integer"
            layout="Layout" />
</target>

Example configuration that buffers LogEvents and sends entire batch on error LogEvent:

  <target xsi:type="AutoFlushWrapper" name="MailErrorFlush"
    condition="level >= LogLevel.Error"
    flushOnConditionOnly="true">
     <target xsi:type="BufferingWrapper" name="MailBuffer"
       bufferSize="50"
       overflowAction="Discard">
        <target xsi:type="Mail" name="MailTarget" />
     </target>
  </target>

smtpAuthentication="Basic" enables use of NetworkCredentials for login, which can be used for sending OAuth ClientId (smtpUserName) and OAuth ClientSecret/AccessToken (smtpPassword). Consider to set From-address same as the username to reduce chance to be seen as spam.

<nlog xmlns="http://www.nlog-project.org/schemas/NLog.xsd" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
      xsi:schemaLocation="http://www.nlog-project.org/schemas/NLog.xsd NLog.xsd">

  <targets>
    <target name="gmail" xsi:type="Mail"
            smtpServer="smtp.gmail.com"
            smtpPort="587"
            enableSsl="true"
            smtpAuthentication="Basic"
            smtpUserName="user@gmail.com"
            smtpPassword="password"
            from="user@gmail.com"
            to="recipient@example.com"
            cc="alice@example.com;bob@example.com;charlie@example.com"
          />
  </targets>

  <rules>
    <logger name="*" minlevel="Debug" writeTo="gmail" />
  </rules>
</nlog>