July 2021 Summaries

If you want to protect your deliverability, it’s essential to separate your transactional and promotional email using Postmark's Message Streams. Transactional streams handle invoices, password reset emails, while broadcast message streams are for newsletters and promotions. To process mail fast and reliably, you must specify whether the email is a transactional or broadcast message. When sending via SMTP, users could previously only use a single option to specify a Message Stream by authenticating with a Server Token and setting the `X-PM-Message-Stream` header. However, this was limited by some SMTP clients not allowing custom headers. To fix this issue, Postmark introduced Custom SMTP Tokens for all Message Streams, which allow users to authenticate and send email via their chosen Message Stream without modifying email headers. These tokens can be generated for each outgoing Message Stream, providing an additional layer of security and flexibility.

We've noticed a trend where some customers see sudden ISP Blocks and soft bounces from Google only for specific email messages, hinting at issues with the content and links. Gmail's bounce notifications suggest that the issue might be related to suspicious content or links within the message. Upon closer inspection, we found that all the blocked messages included free URL shorteners, particularly bit.ly links, which are commonly used by spammers to hide malicious websites and files. To avoid similar issues, we recommend using original URLs whenever possible, especially when tracking links in your emails, and consider using reputable link tracking services like Postmark's high-reputation domain to optimize deliverability. Additionally, valid HTML, CTAs, and plain text copies can also impact email deliverability. There are best practices guides available for transactional and broadcast sending that can help improve deliverability.