Summary
Test emails with 'TEST' in the subject line are frequently sent to the spam folder due to a variety of factors: the word 'TEST' is a common spam trigger used by malicious senders, modern spam filters leverage machine learning to identify such patterns, filters evolve over time without announced changes, and bulk mailings using 'TEST' can negatively impact sender reputation. The consensus is to avoid 'TEST' in subject lines, even for testing, and to use realistic subject lines to maintain deliverability.
Key findings
- Common Spam Trigger: The word 'TEST' is a widely recognized spam trigger, causing email providers like Outlook to flag messages with this term.
- Machine Learning Filters: Modern spam filters utilize machine learning, which constantly adapts and learns to identify spam patterns. What worked previously may no longer be effective.
- Evolving Filters: Email providers update their spam filters frequently and often without public announcement, necessitating continuous adaptation of email practices.
- Negative Reputation Impact: Sending bulk emails with 'TEST' in the subject line can harm sender reputation, leading to more emails being flagged as spam.
Key considerations
- Avoid 'TEST' in Subject Lines: Refrain from using the word 'TEST' or variations thereof in email subject lines, even for internal testing purposes.
- Use Realistic Subject Lines: Employ realistic and relevant subject lines for all emails, including test emails, to avoid triggering spam filters.
- Monitor Deliverability: Continuously monitor email deliverability rates and adjust practices as needed to adapt to evolving spam filtering techniques.
- Alternative Testing Methods: Implement alternative email testing methods that do not rely on spam-triggering terms in the subject line.
What email marketers say
8 marketer opinions
Test emails with 'TEST' in the subject line often land in the spam folder in Outlook because email providers like Outlook have updated their spam filters to flag the term as a common spam trigger. Senders should avoid using 'TEST' and opt for more realistic subject lines, even for test emails.
Key opinions
- Spam Trigger: The word 'TEST' in a subject line is a common trigger for spam filters, including those used by Outlook.
- Evolving Filters: Email providers are constantly updating their spam filters, so what worked in the past may not work now.
- Sender Action: Using 'TEST' in the subject line should be avoided, and realistic subject lines should be used instead.
Key considerations
- Subject Line: Carefully consider the subject line of your emails, even test emails, to avoid triggering spam filters.
- Filter Updates: Be aware that email provider spam filters change over time, and adjust your practices accordingly.
- Testing Methods: Explore alternative methods for testing emails that don't rely on using 'TEST' in the subject line.
Marketer view
Email marketer from Mailjet shares that using words like 'test' in your subject line can trigger spam filters. It’s best to use real subject lines even for test emails to avoid being flagged as spam.
12 Nov 2024 - Mailjet
Marketer view
Email marketer from Campaign Monitor responds that subject lines that include the word test are flagged by Outlook as spam because spammers send out test emails frequently.
30 Sep 2023 - Campaign Monitor
What the experts say
4 expert opinions
Test emails with 'TEST' in the subject line are increasingly being flagged as spam due to a combination of factors: the historical association of 'TEST' with spam campaigns, the evolving nature of machine learning-based spam filters, and the general lack of transparency regarding filter updates. Experts suggest avoiding 'TEST' in subject lines altogether to maintain deliverability.
Key opinions
- Negative Association: The term 'TEST' in subject lines has a negative association with spam, leading filters to flag it as suspicious.
- Machine Learning: Spam filters are based on machine learning and adapt over time, meaning previously acceptable practices may no longer be effective.
- Lack of Transparency: Email filter maintainers typically do not announce changes, making it difficult to anticipate and adjust to new filtering rules.
Key considerations
- Avoid 'TEST': Refrain from using 'TEST' in subject lines, even for internal testing.
- Adapt to Change: Recognize that email deliverability is a dynamic landscape and adjust your practices accordingly.
- Proactive Testing: Implement alternative methods for testing email campaigns that do not rely on spam-triggering terms.
Expert view
Expert from Spamresource highlights that using 'Test' in the subject line is a common mistake that triggers spam filters. Due to spammers commonly using such terms, these emails are often flagged as unwanted or harmful.
15 Sep 2021 - Spamresource
Expert view
Expert from Word to the Wise, Laura Atkins, explains that filters have learned over time to identify the word 'test' in the subject line as suspicious. Even if used legitimately for testing, the association with spam has caused these emails to be treated as such.
13 Jul 2023 - Word to the Wise
What the documentation says
3 technical articles
Test emails with 'TEST' in the subject line are routed to the spam folder due to filters identifying them as potentially unsolicited and harmful. This is because spammers often use similar subject lines. Using generic terms like 'Test' without meaningful content further increases the likelihood of being flagged as spam and impacting the sender's reputation.
Key findings
- Unsolicited Email: Including 'Test' or 'Testing' in the subject line can be flagged as unsolicited email.
- Sender Reputation: Sending test emails with 'Test' in the subject line can negatively affect your sender reputation.
- Suspicious Subject Lines: Spam filters look for suspicious subject lines, including generic terms like 'Test'.
Key considerations
- Avoid 'Test': Do not include 'Test' or 'Testing' in your subject lines.
- Meaningful Content: Ensure your emails have meaningful content, and avoid generic terms in the subject line.
- Protect Reputation: Take steps to protect your sender reputation by avoiding practices associated with spammers.
Technical article
Documentation from Litmus explains that spam filters look for various factors, including suspicious subject lines. Using generic terms like 'Test' without meaningful content can significantly increase the likelihood of being flagged as spam.
30 Jan 2024 - Litmus
Technical article
Documentation from Microsoft Support explains that including 'Test' or 'Testing' in the subject line can be identified as unsolicited email by the Junk Email Filter, which will automatically send the messages to the Junk Email folder.
11 Mar 2022 - Microsoft Support
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