An update to my issue here.
Thank you for your inquiry.
I am preparing a sample application for you to test your scenario with real time data before upgrading your actual application. I will attach the sample as soon as it is prepared.
As you may know Aspose.Email.Mail.
[MailMessage](http://docs.aspose.com/display/emailnet/MailMessage+Class) implements IDisposable. So according to the general rule, the MailMessage should be declared and instantiated in a using statement. I have tested the latest build on similar lines and I have learned that a file cannot be deleted if it has been added as an attachment and the MailMessage object isn’t disposed yet. As soon as the program control leaves the using block, the file can be deleted.
Regarding the question in your second post, I will get back to you on that.
Right, but you cannot use a using block with SendAsync, correct? The client object is able to go out of scope before it is actually sent.