Why do ISPs reject email at RCPT TO command and send abuse reports?
Summary
What email marketers say11Marketer opinions
Email marketer from SendGrid explains that hitting spam traps can immediately damage sender reputation, potentially leading to rejections at the RCPT TO stage.
Email marketer from NeilPatel.com explains that poor sender reputation, marked by high spam complaints, can cause ISPs to reject emails even before delivery attempts.
Email marketer from Postmark states that missing or misconfigured email authentication records (SPF, DKIM, DMARC) can cause ISPs to flag emails as suspicious and reject them.
Marketer from Email Geeks shares it may be a spam trap, but it may also be that the sender or sending IP is not welcome. There may be reasons why it rejects at RCPT TO and not before.
Email marketer from StackOverflow shares that the receiving server may be using a real-time blacklist (RBL) and your sending IP address is listed on it, causing immediate rejection.
Email marketer from SparkPost highlights that low engagement rates (opens, clicks) can signal to ISPs that the sender is not sending relevant emails, potentially leading to rejections and spam filtering.
Email marketer from MailerQ shares that greylisting can lead to temporary rejections at the RCPT TO stage, as the server temporarily refuses to accept the email to filter spam.
Email marketer from Reddit shares that some ISPs use spam traps to identify senders who are not practicing proper list hygiene, leading to immediate rejections and abuse reports.
Marketer from Email Geeks suggests that SPFBL expects the sender to stop sending to the email address that generated the report, whether it is a manual complaint or a rejection. He recommends doing that and then looking elsewhere.
Email marketer from Mailjet explains that rejection at RCPT TO happens before the message body is transferred. This can be due to reputation issues with the sending IP or domain, or because the recipient is on a blocklist.
Email marketer from Litmus says that poor list hygiene, including sending to invalid or inactive email addresses, can increase bounce rates and spam complaints, leading to ISPs rejecting emails.
What the experts say4Expert opinions
Expert from SpamResource states that a low sender reputation, derived from high complaint rates, blacklist listings, and spam trap hits, leads ISPs to reject email during the SMTP handshake at RCPT TO.
Expert from SpamResource explains that sending email to invalid addresses or known spam traps results in rejections and abuse reports, as it signals poor list hygiene and potential spamming practices.
Expert from Word to the Wise explains that being listed on public or private blocklists due to spam-like activity can lead to immediate rejections at the RCPT TO command as ISPs consult these lists during the SMTP transaction.
Expert from Word to the Wise mentions that abuse reports generated via feedback loops (FBLs) directly notify senders of recipients marking their mail as spam, prompting ISPs to possibly reject future emails from that sender if the issue is not addressed.
What the documentation says4Technical articles
Documentation from Google Postmaster Tools explains that high spam complaint rates will negatively affect your sender reputation and lead to emails being rejected or sent to spam.
Documentation from ietf.org defines the RCPT command and explains that servers can reject recipients based on local policy, spam filtering, or other criteria before accepting the message data.
Documentation from DMARC.org explains that DMARC policies enable domain owners to instruct receiving mail servers on how to handle emails that fail authentication checks, including rejecting them.
Documentation from Microsoft explains that they may reject emails at the connection level or RCPT TO level if they detect spam-like characteristics or if the sender's IP address has a poor reputation.