For those running web apps and websites with transactional emails, how much do they affect your server?

I'm doing a little research on the matter, because I am genuinely curious how do transactional emails affect server load and resources? I guess to help answer the question, I'm looking for the following:

• How many emails do you send out on a monthly basis from transactions? (Sign-ups, achievements, that kind of stuff)
• How does it affect your server load? Do you find that you have to dedicate a separate SMTP server box?
• How have you optimized for transactional开发者_如何学Python emails?
• Would it have been easier to get a hosted solution?

Appreciate any responses!

I send about 2k a month (low) and email sending isn't really resource intensive until you hit silly high numbers.

Even with a volume this low I outsource it. Why? It makes it much easier to get better delivery rates, and makes it easier to track bounces, spam reports, all that other fun stuff. They also handle things like whitelisting and throttling the amount of e-mail sent to a single ISP so it doesn't all get rejected based on volume alone.

I worked on a project (in health care) that sent many thousands of short emails a day, both to computer users and pager users (stuff like "Your patient's lab results are ready.")

The overhead for sending email on your web server and SMTP server is truly tiny. If you only have one machine you'll be fine. If you can stand up a separate virtual machine to handle your email, or use the SMTP server furnished by your email service, you'll have greater robustness.

But if you use an email service's SMTP, you'll have to convince them that you're not cranking out spam.