Bulk Email Sending through Asp.Net application : Best Practice Recommendations?

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.NET

IIS

SMTP

Exchange-Server

Hope you all are fine.

I have an application which requires to send 1500-2000 emails with attachment to the same number of customers. My Question is "What would be best practice to achieve that efficiently?"

Whether
1)It can be done efficiently by organization's email account - "NoReply@domain.com" . -If yes, then whether i have to configure IIS's SMTP service and how it will be done or is there some other way. -Or I should install some additional hardware in my intranet.

2)It can be done efficiently by 3rd party email sending providers. If Yes, what are best options for it to be used their API for ASP.Net application to send bulk emails.

-Please Suggest