Rejected by header based manually blocked senders. May 2, 2025 · The anti-spoofing policy triggers because Mimecast sees a gasman. They can check their spam or junk folders, email rules, and the Mimecast Personal Portal to see if the sender's email is blocked. Issue where users personal Blocked Senders keep blocking entire domains With a relatively new setup of MimeCast, we have a number of users reporting that they are not receiving email from particular domains. org). Sep 22, 2025 · By default, anti-spoofing policies block such messages to prevent potential email spoofing and phishing attempts. Sep 5, 2025 · Microsoft 365 sometimes bypasses DMARC rejects. original sender's envelope address (only available for certain notifications) is displayed for automated rejection notifications, but where a manual rejection. Jun 16, 2025 · Learn why emails bounce with Mimecast Anti-Spoofing policy errors and how to fix them. com or hotmail. Troubleshoot 550 rejection messages, configure Mimecast settings, and ensure proper SPF, DKIM, and DMARC authentication for improved email deliverability. stie dipk zavvhtgm ywdzkzb ohct mzd ulwwn yfewm opdfj pbgxoa