Transactional emails typically refer to the emails that your website send out that are administrative in nature and are sent after a certain event has occurred: new user registration, password resets, order confirmations, shipping notifications, and on and on. They are typically not marketing emails.
You may discover at some point that your mail is not getting delivered, and is being marked as spam. This may lead to more customer service calls, bad reviews, complaints…after all, the email your website sends typically contain important information.
Why is this happening?
Getting marked as spam can happen for a number of reasons, but if you’re sure you’re not sending marketing email, then the most likely one is that the server your website is hosted on (and is sending mail from) is not recognized as a safe IP address to accept email from. Your IP may not have a history (or worse — it may have belonged to a spammer before you got it) and that makes it suspicious to many email providers. Yahoo! and Hotmail are particularly touchy, it seems.
Or, you could rely on your own email provider to send the mail — presumably, you don’t have issues sending your own work email, so as long as you continue to not send actual spam, you should be able to send transactional email through it too — in theory. Email providers will have daily sending limits, limits on the number of recipients of a single email, and limits on the number of undeliverable emails you send — running afoul of any of those limits will risk getting your account suspended or terminated. Even paid providers, like Google Apps for Work, are going to have sending limits. If you still want to go this route, how to configure your site is outside the scope of this post, but you should be able to find resources on how to do it for your specific set up.
Another option you have is to use an email-sending service like Mandrill or Amazon SES. These services come at a low cost, though Mandrill is free for the first 12,000 messages per month — perfect for most small business websites. Again, setup is outside the scope of this post, but if you use WordPress, there are plugins to integrate with both (for Mandrill, for Amazon SES), making them very easy to set up. This is my highest recommendation, because these services are built for volume, reliability, and high deliverability.
Please reach out for a quote if you would like assistance integrating Mandrill or Amazon SES with your website!
Share your tips for improving the deliverability of your email in the comments — please also share if you have experience with Mandrill, Amazon SES, or another service as well!