What could cause a sudden increase in transactional email bounce rates, and how can it be diagnosed?

Email marketer from Mailjet explains that several factors can cause high bounce rates, including sending to outdated or invalid email addresses, spam traps, or when recipients mark emails as spam, damaging your sender reputation. The email might be flagged as spam if the content is suspicious.

Email marketer from Email Geeks shares that issues with Hotmail/Outlook or Comcast are not related to Google/Yahoo requirements.

Email marketer from GMass explains that implementing email authentication protocols (SPF, DKIM, DMARC) helps establish trust with email providers and can prevent emails from being marked as spam, reducing bounce rates.

Email marketer from HubSpot explains that bounce rates can be hard bounces (permanent) or soft bounces (temporary). Hard bounces are due to invalid email addresses and soft bounces are due to temporary problems like a full inbox or server issues.

Email marketer from Email Marketing Forum shares that examining bounce codes and working with your ESP to understand the reasons for bounces is essential for diagnosing and addressing the root cause.

Email marketer from Constant Contact explains that to reduce bounce rates, you should regularly clean your email list to remove invalid addresses, use double opt-in for subscriptions, authenticate your email, and monitor your sender reputation.

Email marketer from Litmus explains that maintaining list hygiene by regularly removing inactive subscribers and validating email addresses can prevent sending to invalid addresses and improve sender reputation.

Email marketer from ZeroBounce shares that using an email verification service to validate email addresses before sending campaigns helps identify and remove invalid or risky addresses, preventing bounces and protecting sender reputation.

Email marketer from Reddit shares that sudden bounce increases are caused by list decay, changes in spam filtering policies by ISPs, or deliverability issues related to domain reputation.

Email marketer from Sendinblue explains that high bounce rates happen when sending emails to invalid or non-existent email addresses and using outdated email lists. They also state that spam filters and sender reputation play a huge part.

Expert from Email Geeks explains that rejection messages will start with three digits and suggests contacting the ESP's support for help, including providing sample rejection messages.

Expert from Email Geeks explains that to understand bounce rates, it's important to examine the actual rejection messages, including the domain and IPs being sent from and where they're being rejected.

Expert from Spam Resource (Steve Linford) shares that sudden bounce rate increases are often caused by being added to a blocklist. Blocklisting prevents delivery, resulting in bounces, and diagnosis involves checking if your sending IPs or domains are listed on common blocklists.

Expert from Word to the Wise (Laura Atkins) explains that bounces fall into a few major categories, temporary failures, permanent failures, and block bounces, and it's important to differentiate between them to diagnose the root cause of the bounce. Checking the SMTP codes are necessary for diagnosis

Documentation from Microsoft explains that Outlook.com provides feedback loop mechanisms and sender support resources to help diagnose and address deliverability issues, including bounces, that can impact sender reputation and email placement.

Documentation from SparkPost explains that bounces are classified based on SMTP response codes from the receiving mail server. This classification helps diagnose the reason for the bounce, categorizing them as hard, soft, or technical failures.

Documentation from RFC Editor explains that SMTP (Simple Mail Transfer Protocol) uses a series of error codes to identify the reason an email bounced. The codes are three digits long where the first number indicates whether the response is good, bad, or incomplete. Looking into the specific code is necessary for diagnosin.

Documentation from Amazon AWS explains that Amazon SES provides multiple methods for handling bounces, including using Amazon Simple Notification Service (SNS) to receive notifications, automatically suppressing addresses from future sends, and providing a feedback loop for bounce events.

Documentation from Google explains that using Google Postmaster Tools to monitor sender reputation, spam rate, and feedback loop data is essential for identifying deliverability issues that may contribute to higher bounce rates.