Sending E-mail messages from Microsoft Dynamics AX could be a bit tricky.
The most recommended way to do so is by using the standard mail mechanism built in the system.The Email sending status form (based on tableSysOutgoingEmailTable) and the E-mail distributor batch job.
But if you want to send email with attachments and more advance options, you should do so with .NET Framework, and the System.Net.Mail object.
First of all, make sure you have a correctly configured SMTP server.
Go to Administration -> Setup -> E-mail parameters and fill the required settings:
Then, use this code sample: