I have just signed up to sendgrid on the free plan (to test things out, so we can upgrade when we launch our product).

This is just a quick call to the community to see which API you guys are using. I am using the PHP SDK if that makes any difference.

SendGrid recommends the SMTP API (http://sendgrid.com/docs/Integrate/) and I have integrated with Swiftmailer, which provides pretty good SMTP support to a PHP application.

Having said that, I have used Swiftmailer to send mail using Gmail's SMTP server via my pc (localhost) and it always seems to be quite slow (compared to working with REST interfaces).

I will also prefer not to run a local mail server at them (there's already enough work in coding, tuning and running nginx and various databases).

What do you guys use in production and why? I am planning to run my app on Linode in production if that makes a difference.

Cheers :)