Sending bulk notification emails without blocking

For my client's custom-built CRM, I want users (technicians) to be notified of changes to marked cases via email开发者_StackOverflow社区.

This warrants a simple subscription mapping table between users and cases and automated emails to be sent every time a change is made to a case from within the logging method.

How do I send 10-100 emails to subscribed users without bogging down my logging method? My SMTP server is on a peer on my LAN, so sends should be quick, but ideally this should be handled by an external queuing process.

I can have a cron job send any outstanding emails every 10 minutes, but for this specific client cases are quite time-sensitive and instant notification (as instant as email can be) would be great.

How can I send bulk notification emails from within ASP.NET MVC without bogging down my logging method?

Back in 2007 I was asked to look into a case where Web Server would suddenly freeze and start sending 503 errors and come back after a few minutes. Cutting a long story short it turned out at the end that it was sending email which was blocking the server (in addition to some bad code).

Basically Microsoft's SMTP server is implemented as a single-thread service - last I checked. This will mean that all your valuable ASP.NET threads serving requests will have to queue to a single thread monolithic application to send a not so urgent email. You need to decouple your web site from sending emails - that is what everyone does and there is a good reason for it.

Write your emails to a queue and have a process reading and sending emails.

Sending emails from an ASP.NET application is not a good idea as it might monopolize valuable server resources. A better solution would be to setup a Windows Service to perform this task or even write a Console application which could be scheduled to run with Windows Scheduler. Quartz.NET is a good solution you might take a look at allowing you to schedule jobs.

If you want those email sending to be triggered from within a particular controller action you could also have a separate WCF service which could be invoked asynchronously.