How does Gmail handle unauthenticated or poorly aligned mail?

Gmail handles unauthenticated or poorly aligned mail with increasing suspicion. Messages failing SPF or DKIM checks may be rejected outright, especially from bulk senders. Those with partial authentication but poor alignment face aggressive spam filtering.

Alignment refers to whether the domains in SPF and DKIM match the From header domain. Gmail expects either SPF or DKIM alignment for DMARC to pass. Misaligned authentication, where checks pass but domains do not match, weakens trust signals.

Gmail may also display warning banners on emails with authentication issues, alerting users that the sender could not be verified. This damages recipient trust even if the message reaches the inbox. The clear message from Gmail is that authentication is not just about deliverability but about being recognized as a legitimate, trustworthy sender.