MAIL FROM record is not aligned.

I am confused that you ask:

Is there something missing in my DNS records?

But then say:

I don't have custom domain.

Do you have a domain or not?

For sending emails, I would recommend Simple Email Service (SES). You can make API call from JS to the SES service to send your emails. Here is a link to how SES works.

Be aware, if what you are sending is spam or is reported by the recipients as spam, it will catch up with you (see the feedback loop in the above link).

Hope this helps!