Optimal Droplet Size for Sending 10,000 Emails Daily Using PHP

To determine the right droplet size to send 10,000 emails daily through PHP, several factors need to be considered, including the email sending method, rate limits, resource requirements, and email content.

Factors to Consider

When setting up a droplet for email sending, various technical and operational aspects must be taken into account. These elements can significantly impact the effectiveness of your email sending process.

Email Sending Method

Local Mail Server vs External Service: Depending on whether you are using a local mail server like Postfix or an external service like SendGrid, Mailgun, etc., the requirements can differ. Local servers may require more resources for handling SMTP connections and queuing.

Rate Limits

Provider Rate Limits: Many email providers impose rate limits. For instance, if your provider allows 100 emails per hour, stagger the sending process to meet your daily goal without reaching the maximum limit.

Resource Requirements

CPU and Memory: Sending a large number of emails can be CPU-intensive. A droplet with at least 1 CPU and 1-2 GB of RAM should be sufficient for moderate usage. Network Bandwidth: Ensure the droplet has sufficient bandwidth to handle the outgoing emails. Most small droplets with 1 TB of transfer should suffice for 10,000 emails.

Email Content

Email Size and Complexity: The size and complexity of the emails, including whether they are plain text or HTML with images, can affect the sending speed and resource usage.

Recommendations

Small Droplet: A droplet with 1 CPU and 1-2 GB of RAM should be sufficient for sending 10,000 emails in a day, especially if you are using an external email service. Medium Droplet: If you are using a local mail server or expect high traffic, consider a medium droplet with 2 CPUs and 4 GB of RAM for better performance and reliability.

For sending 10,000 emails in a day through PHP, a small to medium-sized droplet should suffice, particularly if you are using a reliable external email service. Always ensure to test and adjust based on your specific needs and the performance of your application.

Conclusion

The computer required to deploy an email can be surprisingly small. For example, a $10/month droplet from DigitalOcean has 1 GB of memory and can process about 100 billion CPU instructions every second. Deploying an email can be achieved on a machine with one hundredth of this specification.
An email is roughly 200 kB, meaning that a droplet's 2 TB monthly bandwidth quota will cover roughly 300,000 emails a day.
Note that running an email server is tricky. There’s a good article on why you might not want to do this published by DigitalOcean.