Why are Gmail emails flagged with 'Images are hidden, this message might be suspicious' banner?

Email marketer from HubSpot shares that sending emails to outdated, inactive, or invalid email addresses can result in high bounce rates and negatively affect sender reputation, causing Gmail to flag emails as suspicious.

Email marketer from Sender Score says that if you have a poor sender score, which is an indicator of your IP's reputation, you will be more likely to be flagged as suspicious. Regularly monitor your sender score for signs of issues.

Email marketer from Gmass explains that a high spam complaint rate from Gmail users directly impacts sender reputation, leading Gmail to flag emails with the warning banner.

Email marketer from Reddit explains that suspicious or shortened URLs within the email body can trigger Gmail's warning banner, especially if the linked domain has a poor reputation or is associated with spam.

Email marketer from Stack Overflow shares that using spam-like keywords, excessive capitalization, or misleading subject lines can cause Gmail to flag emails as suspicious.

Email marketer from Litmus states that sending emails from inconsistent IP addresses, especially if they're not authorized in the SPF record, can cause Gmail to flag messages as suspicious.

Email marketer from Email Geeks notes the banner appearing in a cold outreach email containing only a tracking pixel and speculates whether Gmail might be penalizing tracking in personal or 1:1 emails.

Email marketer from Mailjet Blog shares that a poor sender reputation, often resulting from high bounce rates, spam complaints, or being listed on blacklists, can lead to Gmail flagging emails as suspicious.

Email marketer from Email Geeks shares experience of seeing the same Gmail error due to broken image hosting links or inaccessible images.

Email marketer from Neil Patel's Blog responds that Gmail may flag emails with a suspicious banner if the sender's email authentication (SPF, DKIM, DMARC) is not properly configured, making the email appear less trustworthy.

Expert from Word to the Wise shares that several issues cause the warning, including missing or broken authentication, using short URLs, or the URL having a bad reputation.

Expert from Email Geeks believes Google might be changing their filtering mechanisms and how they communicate these changes to users.

Expert from Email Geeks suggests checking the reputation of the image URLs and CDNs used in the emails.

Expert from Email Geeks suggests that issues with AWS image hosting can often be resolved by using branded URLs instead of the default s3.* moniker.

Expert from Word to the Wise explains that this could be Gmail testing a new user interface or changes to how they're displaying trust indicators. The cause could also be issues with authentication or content.

Expert from Email Geeks theorizes that Gmail may be treating welcome emails differently due to high spam report rates and unusual patterns, balancing the desire to deliver wanted messages with overall reputation considerations.

Expert from Email Geeks mentions seeing the Gmail "Images in this message are hidden..." banner issue reported a couple of times recently, suggesting it's a new but not widespread issue.

Documentation from RFC explains that an incorrectly configured SPF record, such as one that is too broad or contains errors, can cause Gmail to treat emails with suspicion, as it can't properly verify the sender's legitimacy.

Documentation from DMARC.org clarifies that when DMARC policy fails (e.g., SPF and DKIM don't align), Gmail may flag emails as suspicious to protect users from potential phishing or spoofing attacks.

Documentation from Google Support explains that Gmail displays warnings if senders don't follow Gmail's sender guidelines, which include authenticating emails, avoiding spammy content, and maintaining a good sender reputation.

Documentation from Microsoft explains that emails are automatically flagged due to safety or privacy settings, users can configure their filtering rules which causes emails to be flagged.

Documentation from DKIM.org shares that if the DKIM signature is invalid or missing, Gmail cannot verify the email's authenticity, increasing the likelihood of it being flagged as suspicious.