Why does Gmail say it cannot verify the sender and mark the email as spam?

Email marketer from SendPulse responds that low engagement rates (e.g., few opens and clicks) can negatively affect sender reputation over time. Gmail interprets low engagement as a sign that recipients don't want the emails, increasing the likelihood of spam classification.

Email marketer from SuperOffice suggests that if you're sending a large volume of emails, using a dedicated IP address and properly warming it up is crucial. Without a dedicated IP and a gradual warm-up, Gmail is more likely to see the email as unsolicited and filter it as spam.

Email marketer from Email Marketing Forum comments that using spam trigger words (e.g., 'free,' 'guarantee') in the email subject or body can increase the likelihood of Gmail classifying the email as spam. Gmail's spam filters are designed to identify and filter out such content.

Email marketer from Reddit explains that if a domain has a strict DMARC policy (e.g., p=reject), and the email fails SPF and DKIM checks, Gmail will likely reject or mark the email as spam, as it's instructed to do so by the domain owner.

Email marketer from Litmus shares that poorly formatted HTML emails, missing text versions, or overly large images can trigger Gmail's spam filters. Gmail prefers well-structured emails with both HTML and text versions.

Email marketer from EmailOnAcid shares that if the sending IP address or domain has a poor reputation (e.g., listed on blocklists), Gmail is more likely to flag emails as spam. This is because Gmail associates the sender with previous spam activity.

Email marketer from StackOverflow notes that a missing or incorrect reverse DNS (PTR) record can negatively impact email deliverability. Gmail uses PTR records to verify that the sending IP address is associated with the sending domain, and its absence can lead to spam classification.

Email marketer from Mailjet shares that Gmail uses authentication protocols (SPF, DKIM, DMARC) to verify the sender's identity. If these are missing or misconfigured, Gmail might flag the email as spam as a protective measure against phishing and spoofing.

Email marketer from Quora notes that if emails don't have a clear and easy-to-use unsubscribe link, recipients are more likely to mark them as spam. High spam complaint rates negatively impact sender reputation and can lead to Gmail filtering emails.

Email marketer from Hubspot shares that inconsistent email sending volume can raise suspicion with ISPs like Gmail. Sudden spikes in email volume, especially from a new IP address, can trigger spam filters because it's a common tactic used by spammers.

Expert from Spam Resource explains that Gmail often flags emails as spam when authentication checks, such as SPF, DKIM, and DMARC, fail. This is a primary indicator for Gmail that the sender may not be who they claim to be, leading to a higher likelihood of spam classification.

Expert from Word to the Wise explains that email warming is crucial when setting up new servers or IP Addresses to avoid spam filters. Sending emails from servers that haven't been warmed up often leads to emails being marked as spam.

Expert from Word to the Wise shares that Gmail uses list hygiene as a contributing factor in its spam filtering decisions. Sending to old or unengaged email addresses can result in Gmail marking your email as spam.

Experts from Email Geeks confirm that the SPF record is messy and has to be fixed. This includes issues like extra backslashes and broken strings and also SFMC includes. They mention unix-y escaping of the " inside of a quoted string.

Expert from Email Geeks recommends checking the email headers ('Show Original' in Gmail) for summary information and suggests the problem is related to a broken SPF record which is missing the Google include and contains extra characters.

Expert from Email Geeks suggests the grayed out icon and 'cannot verify sender is not a spammer' message indicates an issue with email authentication.

Documentation from Microsoft explains that similar to Gmail, their email services also heavily rely on sender authentication methods. If SPF, DKIM, and DMARC records are not correctly configured, or if the domain has a history of abuse, emails are more likely to be classified as junk or spam.

Documentation from Google Support explains that Gmail can't verify the sender when email authentication methods like SPF and DKIM aren't properly set up. This lack of verification can lead to Gmail marking the email as spam.

Documentation from DKIM.org clarifies that a valid DKIM signature confirms that the email content hasn't been altered in transit. Without it, Gmail has no cryptographic assurance that the email is genuine, making it more prone to spam filtering.

Documentation from RFC-Editor details the SPF standard and shows that SPF failures (e.g., 'softfail' or 'fail') can cause receiving mail servers to treat messages with suspicion, increasing the likelihood of spam classification.

Documentation from Spamhaus explains that if the sending server's IP address is listed on a real-time blocklist (RBL) like Spamhaus, Gmail will likely mark the email as spam. These blocklists are used to identify and filter out known sources of spam.