There are several rate limitations and restrictions that you should be aware of when using the v3 Mail Send endpoint.

  • The total size of your email, including attachments, must be less than 30MB.
  • The total number of recipients must no more than 1000. This includes all recipients defined within the to, cc, and bcc parameters, across each object that you include in the personalizations array.
  • The total length of custom arguments must be less than 10000 bytes.
  • Unicode encoding is not supported for the from field.
  • The,, and personalizations cannot include either the ; or , characters.

For more specific, parameter level requirements and limitations, please refer to the v3/mail/send documentation.

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