What are ISP practices for identifying and handling suspicious email?

Marketer from Email Geeks shares that some ISPs provide IPs that they have high confidence are garbage mail, and blocking them is acceptable. He also suggests adding a header to suspect messages to inform Mailbox Providers (MBPs) that the messages are spam.

Email marketer from Litmus explains that ISPs use sophisticated spam filters that analyze various aspects of an email, including the sender's IP address, domain reputation, email content, and user engagement. They recommend senders to test their emails before sending, use a reputable email service provider (ESP), and monitor their deliverability metrics to identify and address any issues.

Email marketer from StackOverflow mentions that ISPs rely heavily on sender reputation to filter spam. This reputation is built over time based on factors such as bounce rates, complaints, and engagement. A poor sender reputation can lead to emails being blocked or sent to the spam folder.

Email marketer from SparkPost answers that ISPs monitor sending volume and frequency from new IPs. A sudden large spike in sending volume can trigger spam filters. They advise new senders to gradually increase their sending volume over time to establish a positive sending reputation.

Email marketer from Hubspot explains that ISPs analyze email content for spam-like keywords and phrases. They recommend avoiding excessive use of promotional language, ALL CAPS, and exclamation points to prevent emails from being flagged as spam.

Email marketer from emailmarketing.org forum explains that ISPs use feedback loops (FBLs) to allow recipients to report spam. Senders who participate in FBLs receive notifications when their emails are marked as spam, allowing them to remove those recipients from their lists and improve their deliverability.

Email marketer from SendGrid shares that ISPs monitor sender reputation based on factors like bounce rates, spam complaints, and engagement metrics. They advise senders to segment their lists, personalize their emails, and actively manage unsubscribes to maintain a positive reputation and improve deliverability.

Email marketer from Quora explains that proper email authentication (SPF, DKIM, DMARC) is crucial for avoiding spam filters. ISPs use these protocols to verify the sender's identity and ensure that the email is not spoofed or forged.

Email marketer from Mailchimp explains that spam filters are triggered by various factors, including high complaint rates, blacklisted IPs, and suspicious content. They recommend senders to use double opt-in, authenticate their emails, and regularly clean their email lists to avoid being flagged as spam.

Email marketer from Reddit shares that some ISPs use honeypots (spam traps) to identify spammers. Sending emails to these addresses indicates that the sender is not practicing proper list hygiene and can result in being blacklisted.

Expert from Spam Resource explains that ISPs and blocklist providers use spam traps (pristine and recycled) to identify senders with poor list hygiene practices. Hitting a spam trap indicates that the sender is either harvesting email addresses or not properly managing their list and can result in severe deliverability penalties.

Expert from Word to the Wise shares that seed lists can be used to test deliverability rates across different mailbox providers. By sending test emails to seed addresses, senders can identify potential blocking issues before widespread sending.

Expert from Spam Resource explains that ISPs assign reputation scores to sending IPs and domains based on various factors, including volume, complaints, and engagement. These scores are then used to determine whether to accept, reject, or filter emails. Good reputation leads to better deliverability, while a poor reputation can result in emails being blocked.

Expert from Word to the Wise shares that participation in Complaint Feedback Loops (FBLs) is vital for understanding how recipients are reacting to your mailings. Monitoring FBLs allows senders to promptly remove complainers from their lists, mitigating the risk of broader deliverability issues.

Documentation from Google explains that Google uses various signals to identify suspicious emails, including user reports, spam traps, and authentication failures (SPF, DKIM, DMARC). They advise senders to monitor their reputation through Google Postmaster Tools and address any issues promptly to avoid being flagged as suspicious.

Documentation from Microsoft explains that their spam filters use a combination of technologies, including content filtering, sender reputation, and machine learning, to identify and block suspicious emails. They also provide guidance on best practices for senders to avoid being flagged as spam, such as authenticating emails and maintaining a clean sending list.

Documentation from RFC outlines mechanisms for reporting unsolicited bulk email (UBE), including spam, to the administrators responsible for the originating network. It suggests that ISPs use these reports to identify and take action against spammers.

Documentation from DMARC.org explains DMARC (Domain-based Message Authentication, Reporting & Conformance) is an email authentication protocol that allows senders to indicate that their emails are protected by SPF and DKIM, and instructs receiving mail servers on how to handle emails that fail authentication. This helps ISPs identify and block fraudulent emails.