What causes a sudden increase in email bounce rates after switching to a new email platform?

A sudden increase in email bounce rates after switching to a new email platform is a multifaceted issue stemming from technical configuration, list hygiene, and reputation factors. Key contributors include the lack of established sender reputation for new IPs and domains, often compounded by failing to implement a proper IP warm-up strategy. Technical setup issues such as incorrect or missing email authentication (SPF, DKIM, DMARC) and DNS records further exacerbate the problem. List quality plays a crucial role, with uncleaned lists containing invalid addresses and a history of suppressed unsubscribes from a previous platform leading to increased bounces. Furthermore, poor list engagement, changes in sending frequency, shared IP reputation, and the presence of 'user unknown' bounces, or being on a blocklist can all significantly impact deliverability. New platforms can also expose underlying list quality issues due to stricter bounce handling or different suppression mechanisms.

A sudden increase in email bounce rates after switching to a new email platform can be attributed to several factors. These include neglecting to warm up the new IP address, resulting in a lack of established sender reputation with ISPs. Poor list hygiene, where the old platform may have suppressed bad addresses but the new one doesn't, exposes invalid emails. Incorrect or missing email authentication settings (SPF, DKIM, DMARC) can lead to rejections by ISPs. Additionally, sharing an IP address means the reputation of other senders can impact deliverability. Drastic changes in sending frequency can also negatively affect reputation. Finally, ensuring a compliant, permission-based email list and correct DNS records is crucial for avoiding high bounce rates.

Experts attribute the sudden increase in email bounce rates after switching platforms to a few key reasons. A likely cause is the presence of 'user unknown' bounces, suggesting invalid users in the email list; for O365 accounts, submitting a support request to Microsoft might help. Additionally, if the previous platform suppressed unsubscribed and bouncing addresses, failing to clean the list before migrating exposes these addresses, leading to higher bounce rates. Furthermore, the new platform's potentially stricter bounce handling or different suppression mechanisms can reveal underlying list quality problems, even if they existed before the switch. Beyond list quality, technical setup issues also contribute to increased bounce rates during platform migration.

Documentation suggests several technical reasons for increased bounce rates after switching email platforms. A primary factor is the lack of established reputation for the new platform's IP address and sending domain; sending high volumes immediately triggers spam filters. Specific SMTP error codes, like 550 5.1.1, point to recipient mailbox issues, indicating more invalid addresses being attempted. Poor list engagement also contributes, as unengaged recipients are more likely to bounce or be marked as spam, especially when sender reputation is unproven. Lastly, being on a blocklist directly increases bounce rates, necessitating regular checks and removal requests.