An analysis of one billion emails processed in January 2026 found that 56.1% were blocked by spam and virus filters, with only 43.9% delivered, according to a 2026 email traffic study. The findings, which include malicious traffic, identify poor sender reputation as a factor in 33.9% of rejected emails, followed by invalid recipient addresses and authentication issues. For businesses relying on email marketing, the data underscores the need for healthy email lists, properly configured sending infrastructure, and a trustworthy sender reputation.
Gmail has set strict requirements for senders, recommending that user-reported spam complaint rates stay below 0.1% and never reach 0.3%. According to Google's sender guidelines, elevated complaint rates can negatively affect inbox placement, and bulk senders with rates above 0.3% may become ineligible for delivery issue mitigation. Since November 2025, Gmail has progressively increased enforcement against messages that fail to meet its sender requirements, including temporary and permanent rejections.
"For years, businesses focused on increasing email volume without always paying the same attention to email list quality and message preparation," said Priscila Gonçalves, CEO of SafetyMails. "Today, having a good offer or relevant content is not enough. If sender reputation is compromised or an email contains technical issues, the entire investment in email marketing can go to waste."
Invalid, disposable, and potentially risky email addresses can lead to unnecessary bounces and other delivery problems. Email verification helps marketers identify problematic recipients before sending campaigns. SafetyMails has studied these issues through its proprietary Email List Quality research, covering different business sectors. However, valid recipient addresses alone cannot guarantee inbox placement; authentication failures, message content, suspicious links, and technical configuration can also affect how emails are handled.
In October 2026, SafetyMails launched MailTester, expanding its email verification services with a tool that analyzes messages before sending. Users generate a dedicated test email address, send their message, and receive a technical report within minutes. MailTester provides a spam risk score from 0 to 100, SPF, DKIM, DMARC, and BIMI authentication checks, SpamAssassin analysis, link and redirect evaluation, security checks, and desktop and mobile previews.
"Email verification is an essential step in reducing risks associated with recipients, but it is only one part of the process," Gonçalves explained. "With MailTester, we want to help marketing professionals identify potential problems before sending their emails, giving them more information to make decisions and protect deliverability."
Available to SafetyMails customers since October, MailTester uses the platform's credit system, with each test consuming 100 credits. The tool helps identify potential technical and content-related issues but does not guarantee inbox placement or replace sender reputation monitoring. The broader implication for the email marketing industry is clear: as filtering tightens, senders must treat list hygiene, authentication, and reputation management as continuous priorities rather than one-time tasks. Failure to adapt risks not only wasted marketing spend but also permanent delivery rejections that can erode customer communication channels.
