When sending an email receive a 504

When sending a batch of emails via EWS we receive a 504 response on the /send endpoint with the message:

The Exchange server is busy and cannot send the message right now. Please try again later.

Endpoint / Log: 

• API Log

Causes

•  504 can be used a throttle mechanism

Resolution

• Slow down the rate at which you are sending emails

Resources:

Outbox

See rate limiting