The answers provided paint a detailed picture of how cold emails are blocked and Gmail's related policies. Blocking is not immediate, taking months (6-12) to fully affect corporate email and often initially resulting in spam folder placement. Gmail is proactively blocking, even threatening permanent shutdowns for violations such as exceeding sending limits (which vary by account type, as detailed in Google Workspace Admin Help docs). Effective strategies include personalization, warming up IPs, list cleaning, authentication (SPF, DKIM, DMARC), and gradual sending increases. Sender reputation, complaint rates, and email engagement are key blocking factors, assessed by Gmail's machine learning (as outlined in the Google Online Security Blog), with user feedback improving spam filters. Blocked emails can generate server error codes (per IETF documentation). Experts highlight the importance of genuine engagement and ongoing policy awareness. ISPs and mailbox providers use diverse metrics for blocking, as outlined by Spam Resource, and Word to the Wise emphasizes engagement's critical deliverability role.

The provided responses indicate that the time it takes for cold emails to be blocked by Gmail and other providers depends on various factors, including sender reputation, email content, engagement metrics, and adherence to best practices. Key strategies for avoiding blocks include personalizing emails, warming up IP addresses, maintaining clean email lists, authenticating domains, and gradually increasing sending volume. Google enforces different sending limits depending on the account type and sender reputation.

The responses highlight that blocking cold emails is a complex process influenced by several factors. It can take months for blocking to impact corporate email significantly, often resulting in emails landing in spam folders initially. Gmail is becoming more aggressive with outbound blocking, including limiting the number of emails sent per day and threatening account shutdowns for violations. Blocking decisions depend on sender reputation, complaint rates, engagement metrics, and ISP/mailbox provider policies. Email engagement significantly affects deliverability, with low engagement increasing the likelihood of emails being blocked or sent to spam.

Google's policies on cold email, as indicated by the provided documentation, include limitations on the number of emails sent per day to prevent spam and abuse, with these limits varying based on account type. Gmail employs advanced machine learning techniques to detect and filter spam by analyzing email content, sender reputation, and user engagement. User reports of spam contribute to the improvement of Gmail's spam filters. When emails are blocked, servers may respond with error codes to notify senders.