PayPal Integration Issue

We have integrated the payment for PayPal and our Nopcommerce site: https://jeenalavie.com/
But we are still getting this warning from PayPal-> PayPal Instant Payment Notification Warning, here's the warning content

Be careful with this message
Swati Mazumder is similar to a name in your organization, but the email address does not belong to your domain or SyncSol Mail couldn’t verify that it actually came from [email protected]. Avoid replying to this email unless you reach out to the sender by other means to ensure that this email address is legitimate.

How can we fix this error?

Where are you seeing the warning?  I don't think it's related to IPN.  Googling that message says it's a Gmail warning.

Hope you are staying safe!

We are a CMMI 3 certified web design company, having 15+ yrs. of the same domain.

I will be glad to assist you, please add me to discuss further.

Also, you can Skype me: cis.scott or email me: [email protected]

thanks
Scott Walter

Hello There,

Hope you are doing well!!

I am glad to assist you with PayPal integration, for further discussion please reach me at this Email:  [email protected] OR Skype me: live:.cid.7c4b11b60f454feb

Awaiting your positive response.

Regards,
Imtiyaz