What could cause a sudden increase in DNS failure and hard bounces in email delivery?

Email marketer from Campaign Monitor explains that server misconfigurations on the sending or receiving side can lead to DNS failures. Issues such as incorrect server settings, firewall configurations, or network problems can prevent proper DNS resolution, resulting in bounce messages.

Email marketer from Email on Acid says DNS issues, such as problems with MX records or DNS outages, can cause email delivery failures and result in hard bounces. Monitoring DNS health helps catch and address these issues proactively.

Email marketer from Litmus explains that a sudden drop in sender reputation, often caused by increased spam complaints or sending to invalid addresses, can lead ISPs to block emails, resulting in a higher bounce rate and DNS failure messages.

Email marketer from Stack Overflow shares that DNS failures can occur due to temporary DNS server outages or incorrect DNS settings on the sender's side. If the sending server cannot resolve the recipient's domain, it leads to delivery failures and bounce messages. It might be a problem with the recipient's DNS server or temporary internet issues.

Email marketer from Gmass explains that incorrect or missing email authentication records (SPF, DKIM, DMARC) can cause recipient servers to reject emails, leading to increased bounces and potential DNS failure messages if authentication checks fail during DNS lookups.

Email marketer from Mailjet Blog explains that sudden drops in deliverability can be caused by issues with your sending reputation, IP address blacklisting, changes in email content triggering spam filters, or technical issues like DNS misconfiguration. Also mentions the importance of monitoring bounce rates and sender reputation.

Email marketer from Reddit shares that bounces can occur due to changes in the recipient's mail server configurations, such as new spam filters or stricter security settings. Temporary glitches on the recipient's server might also cause temporary DNS failures, leading to bounces during the delivery attempt.

Email marketer from SendPulse Blog explains that an increase in hard bounces often points to a high number of invalid or non-existent email addresses in the mailing list. It can also result from recipients marking emails as spam, leading ISPs to block future messages. DNS issues preventing email servers from properly routing the messages can cause an uptick in bounces.

Email marketer from Validity explains that poor list hygiene practices, such as not regularly removing invalid or inactive email addresses, can lead to a high bounce rate. Sending to a large number of invalid addresses can negatively impact sender reputation and increase DNS failure-related bounces.

Expert from Email Geeks recommends using aboutmy.email to do a quick, but fairly thorough, check of DNS and authentication.

Expert from Email Geeks explains that DNS failure in a delivery report generally means they couldn't find the MX for the receiving server, not that the sender's records are bad.

Expert from SpamResource shares that sudden increases in hard bounces and DNS failures can result from being added to blocklists due to spam-like activity. This can stem from sudden spikes in email volume, content triggering spam filters, or compromised accounts sending malicious emails. Getting blocklisted prevents email delivery and can cause DNS lookup failures.

Expert from Word to the Wise says that high bounce rates typically result from sending to old or invalid addresses, which can also impact IP reputation. A sudden increase indicates either a major list importing error, or a high spam complaint rate from valid recipients

Expert from Email Geeks suggests looking at what's common in the bounces (recipient MX, source of emails, particular smarthost cluster) to see if there's a technical reason at the sender's end.

Expert from Email Geeks shares that the usual reasons for DNS failure, other than NXDOMAIN, are DNSSEC or IPv6, so those are something to bear in mind while digging through logs.

Expert from Email Geeks explains that "Hard bounce" is near meaningless when it comes to diagnosis, and suggests getting the actual rejection messages from the ESP.

Documentation from Microsoft outlines that specific SMTP error codes indicate DNS-related issues during email delivery. Error codes like 550 4.4.7 indicate DNS lookup failures that prevent the sending server from finding the recipient's mail server.

Documentation from MXToolbox explains that DNS lookup failures could stem from incorrect MX records, DNS server outages, or DNS propagation delays after changes. If MX records are missing or misconfigured, the sending server cannot locate the recipient's mail server, causing delivery to fail.

Documentation from Google explains that incorrect SPF records can cause deliverability issues. If SPF records are not properly configured to authorize the sending server, recipient servers may reject the email, leading to bounces. It's essential to ensure SPF records accurately reflect all authorized sending sources.

Documentation from RFC 5321 defines that temporary DNS resolution failures (e.g., SERVFAIL, temporary errors) result in deferred delivery attempts. Permanent DNS resolution failures (e.g., NXDOMAIN) lead to hard bounces. An increase in NXDOMAIN errors may indicate issues with recipient domain validity or DNS configuration issues.