API rate limit - needs some more explanations


API rate limit - needs some more explanations


I am using ConstantContact for my email campains with 100000 contacts.

Recently I have decided to send marketing mails through transactional mail mode using API.

For example, I need to send emails with offers in Shirts category to my customers who bought ONLY shirts in last 6 months.

I can get email ids which matches my conditions from the backend and using a utility program coded in C#, loop through the contacts and send email to each email id. But the number of email ids will be more than 20000. So I am confused about the API Rate Limit, which is 10000/day. What it actually means? In my understanding, as I am not accessing contacts from ConstantCoantact list, API call not required, but to send each mail I need to make API calls. So can I send 20000 mails/day in above explained situation? or only only 10000/day? 

Please help


Thanks & Regards,






Thank you for reaching out to Constant Contact's API Support.


Contact Contact is not designed as a transactional email service. Each email needs to be assigned a Contact List in order for the email to be Scheduled. While the Contact List can contain a single email this will eventually cause your account to have an extremely large amount of Contact Lists and you do not want to go over 1000 Contact Lists in the account. You would need to keep deleting the Contact Lists to remain under that number; actually we recommend if possible to stay under 100 lists, but we understand that is not possible for all customers.


Instead your better option is to group all email addresses together into a single list that would receive an email for your shirts and then schedule one email to that Contact List.


As far as the rate limit is concerned how you described it is correct. Each time you submit something to one of our endpoints is considered an API call and that counts against the rate limit of which there are two. One of the limits is 4 calls per second; the other rate limit is 10,000 calls per day. You can create multiple API keys under a single Mashery account, or in specific circumstances we may be able to increase the rate limit. However; sending transactional emails is not one of those circumstances since our system is not designed to work in that manner.


Feel free to post any follow up questions, or if you have any questions that require private information to be divulged feel free to email us at webservices@constantcontact.com.

Jimmy D.
Tier II API Support Engineer
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