A couple of DNS zones were deleted by accident and restored pretty quickly. However now all of those domains are bouncing emails with the following message.
Code:
The response from the remote server was:
550 Please turn on SMTP Authentication in your mail client. mail-lj1-f178.google.com [209.85.208.178]:45603 is not permitted to relay through this server without authentication.
Reporting-MTA: dns; googlemail.com
Arrival-Date: Mon, 21 Jan 2019 14:12:53 -0800 (PST)
X-Original-Message-ID: <redacted>
Final-Recipient: rfc822; [email protected]
Action: failed
Status: 5.0.0
Remote-MTA: dns; mx1.domain.tld (IP redacted, the server for the domain redacted.tld.)
Diagnostic-Code: smtp; 550-Please turn on SMTP Authentication in your mail client.
550-mail-lj1-f178.google.com [209.85.208.178]:45603 is not permitted to relay
550 through this server without authentication.
Last-Attempt-Date: Mon, 21 Jan 2019 14:13:44 -0800 (PST)