spam - Should I use the Reply-To header when sending emails as a service to others?

Question

Suppose we have an application that acts as a middleman, allowing Company A to send reports to their customers.

Company A --> Company B (me)--> Company A's customers

After getting the report we send email notifications to the recipients, but they necessarily originate from our company notifications email address e.g.

joe.bloggs@a.com --> notifications@b.com --> peter@c.com

Now, customers tend to reply to those email notifications, wanting them to go back to whoever sent the report at Company A. Instead, they end up back at our address, notifications@b.com.

A simple solution may be to change the Reply-To header on the notifications we send to the relevant Company A address e.g.

joe.bloggs@a.com --> notifications@b.com [Reply-To: joe.bloggs@a.com] --> peter@c.com

But my main concerns are:

• the complete discrepancy in email address and domain between the From and Reply-To fields might make spam or phishing filters more eager to flag the emails
• not all email clients may respect the Reply-To field when people actually click "Reply", and just use From instead. A lesser concern, unless widespread.

Are these concerns founded at all? Or, are there other concerns I should have?

Answer 1

I tested dkarp's solution with gmail and it was filtered to spam. Use the Reply-To header instead (or in addition, although gmail apparently doesn't need it). Here's how linkedin does it:

Sender: messages-noreply@bounce.linkedin.com
From: John Doe via LinkedIn <member@linkedin.com>
Reply-To: John Doe <John.Doe@gmail.com>
To: My Name <My.Name@gmail.com>

Once I switched to this format, gmail is no longer filtering my messages as spam.