We have an app that sends emails on behalf of our clients. All emails are sent via Sendgrid. As part of this we have verified our email sending domains via DKIM and SPF.
When our clients send email, it is constructed as follows:
from: Tom Smith <email-service@ourserver.com>
reply-to: tom.smith@email.com
This works in the vast majority of cases, but there are situations where the "reply-to" is not being respected - recipients are clicking "Reply" in their email clients and the reply is coming back to us.
Is there something that we are missing here. Do we need to explicitly set a FROM or SENDER header? Or something else?