A developer is investigating why users receive duplicate emails. The application posts messages to an SQS queue; a Lambda function polls the queue and sends email through Amazon SES. During high traffic, duplicates occur. Which of the following could cause the duplicate emails? (Choose two.)

Standard SQS queues offer at-least-once delivery, meaning a message might be delivered more than once. This is a fundamental characteristic of Standard SQS and directly leads to potential duplicate processing by the Lambda function, resulting in duplicate emails. If the SQS queue's visibility timeout is less than or equal to the Lambda function's processing time, the message can become visible again in the queue before the Lambda function successfully deletes it. Another Lambda invocation could then pick up and process the same message, leading to duplicate emails. Standard SQS queues do not guarantee exactly-once processing; that is a feature of SQS FIFO queues. Amazon SES DKIM configuration issues or high bounce rates do not inherently cause duplicate email sending; they relate to email deliverability and reputation.