Hi @suyogp,
Think I replied to your other thread, but in case you didn’t see it, here is my response. Let me know if you have any questions!
Just to make sure we’re on the same page, you’re seeing this error message when attempting to reply to a campaign you sent, correct?
This error message nearly always relates to the mailbox provider that hosts the domain of your sender address (Like Gmail, Outlook, ect), rather than Klaviyo itself. For example, if your website is suyogp.com, and people in your company use @suyogp.com emails with Gmail inboxes, then this would likely instead be a Gmail issue. This error is flagging the reply attempt as potentially malicious based upon suspicious content, sender reputation issues, or a compromised account. Because of this, I’d recommend reaching out to Gmail, or your site’s mailbox provider, and ask them if they can clarify why the reply to them isn’t being successfully received.