Can I configure different account S3 bucket in my account DMS service as endpoint?

Hi, yes, you can:

1. You need to make sure the DMS service access role you specify in the source endpoint has the S3 IAM permissions to write from that bucket. Take a look at Prerequisites When Using Amazon S3 as a Target for AWS DMS: https://docs.aws.amazon.com/dms/latest/userguide/CHAP_Target.S3.html

2. You need to make sure the bucket in the external account allow other accounts to access it. This is accomplished with a bucket policy. See https://repost.aws/knowledge-center/cross-account-access-s3

Hope it helps!

Didier