How Many Emails Can I Send in a Day

How Many Emails Can I Send In a Day?

There is no specific limit on emails per day. However, to ensure a system availability for all customers, both paying and free, there is throttling on inbound emails. This is independent of any throttling done on the sending side. AWS SES, Madrill, and SendGrid all implement throttling when sending messages.

How Do I Know if I’m Being Throttled?

There are two stages to throttling.

1. Message deliver is slowed.

During this stage messages are processed increasingly slower based on the number of emails received. This stage is done without customer notification.

In a worse case scenario, this will result in messages being delayed about 1 minute.

2. Mailsac SMTP server returns a 421 error message.

This indicates that the number of messages received has exceeding the throttling limits and message delivery will need to be retried at a later time.

Throttling Limits

Messages sent to custom domains and private addresses, held by customers on a paid plan, are throttled differently than messages sent to public addresses in the domain.

Throttling of messages on custom domains and private addresses will likely be completely unnoticed by customers, with the exception of customers who are sending messages at the rate of thousands per minute.

My Messages are Missing am I Being Throttled?

Unfortunately, due to the interconnected nature of email, this is not a straightforward question to answer.

In many cases, throttling is implemented on the sender side. Our support team has worked through many issues with mail delivery and identified that SendGrid, Mandrill, and SES all implemented throttling.

Throttling, generally, will not result in missing messages. It could result in the delay of delivery or non-delivery of messages depending on how the sending SMTP server handles 421 Errors.

As someone, with years of debugging and troubleshooting experience, this is how I would approach the topic of missing mail.

  1. Attempt to reproduce the issue using a different source and destination email address.
  2. Check sending SMTP server logs to confirm the message was in fact sent.
  3. Check inbound SMTP server logs. Mailsac exposes parts of these logs to customers on under “Recent Mail Activity Log” on the Usage and Analytics page.
  4. Check the Mailsac Blacklist
  5. Check Mailsac Storage Usage to see if the number of messages I am sending exceed my storage capacity and results in recycling of messages before they are viewed.