We have an existing smtp environment setup in an EC2 instance which is used to send Transactional emails like password reset. Now we have a requirement to send System emails to a large user base in the range of > 1000 emails per day.

First question is: Is Amazon SES delivery reliable ?

Second: Should we use our own SMTP instance or SES ? I Think if we use our SMTP server then sending large number of emails will eventually cause the mails landing in spam.

As the mails are important system emails, and not promotional bulk email. Delivery is a major concern.

2 Answers 2


Use SES. Large swaths of the EC2 netblocks are more or less permanently blacklisted (or severely penalized) by several major email providers. The SES endpoints reside in different netblocks that (at least at the moment) aren't blacklisted on a large scale.

That said, even if your email isn't spam, you need to make sure it doesn't look like spam. Make sure you include unsubscribe links, etc.

  • The current ec2 ip that we are using as smtp has a pretty good reputation and is not blacklisted anywhere. I tried to give SES a spin and added Hotmail and AOL address for verification and guess what, the verification email itself went to spam in both cases.
    – Rishabh
    May 25, 2012 at 13:03
  • 1
    @Rishabh I think they could be classified as SPAM due to email content not due to sender IP. May 30, 2012 at 11:49
  • @MaciekSawicki I subscribed with the production environment of Amazon SES. Had to setup the Domain Keys and other certifications. Now the deliverability seems pretty good. Will test for bulk emails and update ... thanks
    – Rishabh
    Jun 1, 2012 at 8:41
  • We have completely switched SES. There was an issue when of the IPs of SES were blacklisted by Yahoo. Which AWS guys removed as soon as we reported. Other than that SES is working great.
    – Rishabh
    Jun 6, 2014 at 20:19

Existing smtp setup may work for single emails but as soon as you try to send emails in bulk , you run into issues. You need to ensure that your headers are not blacklisted and the email gets delivered in the inbox and not spam folder of the user. Also, the time taken to send an email sometimes is huge which kind of delays the delivery and puts a lot of them in the smtp queue. In addition, sending emails in bulk also takes up other resources like CPU etc of your machine. Amazon SES works very well in all these aspects. So don't hesitate and just switch.

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