Summary
The timing of anti-spam bot link clicks in emails is highly variable, influenced by multiple factors throughout the email delivery process. Some security tools perform immediate link checks to detect malicious content, while others intentionally delay their analysis to evade detection and better gauge user intent. Delays can be caused by ESPs queuing emails, messages being quarantined, third-party content filtering, SMTP server latency, and security appliances performing link rewriting and analysis. The sophistication and purpose of the bot, as well as the configuration of the spam filter, also play a role. Furthermore, some organizations use sandboxes that execute and analyze links after a certain period. Speed is only one aspect of bot detection, as anti-spam solutions also consider patterns in email and link click behavior. Aggressive scanning can occur quickly, potentially affecting sender reputation.
Key findings
- Immediate vs. Delayed: Some bots click links immediately, while others introduce deliberate delays.
- ESP Influence: ESPs queue emails, causing a delay between 'send' and delivery.
- Content Filtering: Third-party content filters and security appliances contribute to delays through rewriting and analyzing links.
- Bot Purpose: Bot behavior is dictated by their sophistication and objectives.
- Pattern Recognition: Anti-spam solutions rely on identifying patterns, not just speed, to detect bots.
- Aggressive Scanners: Aggressive scanners will quickly check links.
Key considerations
- No Complete Identification: It is difficult to accurately identify all server clicks as originating from bots.
- Reputation Impact: Aggressive scanning can negatively affect sender reputation.
- Filter Configuration: Filter's speed depends on it's configuration.
- Network Delays: Overall time can be effected by network delays.
- Potential Quarantining: Potential message quarantining before link checking will impact on the delay.
What email marketers say
12 marketer opinions
The timing of anti-spam bot clicks on links in emails varies significantly. Some security tools click links almost instantly to check for malicious content. However, other systems delay link checks by minutes or hours to avoid detection and to better assess user intent. Delays can also occur due to ESP queuing, quarantining, or third-party content fingerprinting. Some companies use sandboxes that analyze links after a period of time. The timing also depends on the bot's sophistication and purpose. While speed is a factor in bot detection, it is not the only one, as anti-spam solutions look for patterns in behavior.
Key opinions
- Immediate Clicks: Some spam filters and security tools click links immediately to check for malicious content.
- Delayed Checks: Many anti-spam systems delay link checks to avoid detection and assess user intent.
- Platform Impact: High email volume to a single platform can influence bot activity due to content fingerprinting and other filtering processes.
- Variable Timing: Bot click timing depends on the bot's purpose, sophistication, and the specific security measures in place.
- Queue Scanning: Spam bots may hold emails in a queue to scan the links, leading to delayed clicks.
Key considerations
- No Foolproof Detection: Completely identifying all server clicks as bot activity is impossible.
- Sender Reputation: Aggressive scanning of links can impact sender reputation so scan with care.
- ESP Delays: ESPs queue emails before sending them, which can add to the perceived delay in link clicks.
- Pattern Analysis: Anti-spam solutions analyze patterns of behavior, not just speed, to identify bots.
- Quarantine Impact: Messages could be quarantined before inspection, which leads to delays.
Marketer view
Email marketer from Snov.io explains that some services will verify the links within your email almost immediately after sending.
15 Dec 2021 - Snov.io Blog
Marketer view
Marketer from Email Geeks explains that high email volume to a single platform, rather than just a single domain, can lead to bot activity. Content fingerprinting issues at third-party filters or hosting providers can also cause bot activity across domains hosted on those platforms.
17 Apr 2022 - Email Geeks
What the experts say
3 expert opinions
The time it takes for anti-spam bots to click links in emails is influenced by several factors. ESPs queue emails, creating a delay between sending and the email reaching the network. The speed of a spam filter's reaction varies based on its configuration and evaluation criteria. Aggressive scanners may check links quickly, potentially impacting sender reputation.
Key opinions
- ESP Queuing: ESPs queue emails before sending, adding to the perceived delay in link clicks.
- Filter Configuration: The speed of a spam filter's reaction depends on its configuration and evaluation criteria.
- Reputation Impact: Aggressive scanning can cause problems and affect sender reputation.
Key considerations
- Starting Timestamp: Using 'hit send' as the starting timestamp can be misleading due to ESP queuing.
- Filter Variability: Spam filter behavior varies; there is no single standard for reaction time.
- Scanner Aggression: Be mindful of aggressive scanners and their potential impact on sender reputation.
Expert view
Expert from Word to the Wise shares that aggressive scanners can cause problems and affect sender reputation, and that it will check links very soon after a message arrives.
8 Jul 2022 - Word to the Wise
Expert view
Expert from SpamResource explains that how quickly a spam filter reacts can vary depending on the filter's configuration and the specific criteria it's evaluating.
10 May 2025 - SpamResource
What the documentation says
3 technical articles
Delays in anti-spam bot link clicks can stem from various points in the email delivery process. SMTP servers can introduce delays, causing link verification to appear later than expected. Security appliances like Cisco's rewrite and follow links, which can cause scanning delays. Similarly, Proofpoint TAP URL Defense rewrites and analyzes links before routing users, leading to additional delays.
Key findings
- SMTP Delays: SMTP servers can introduce delays in email delivery, impacting the timing of link verification.
- Cisco Scanning: Cisco Email Security Appliance rewrites and follows links, causing potential scanning delays.
- Proofpoint Analysis: Proofpoint TAP URL Defense rewrites and analyzes links, adding delays before routing users to the destination.
Key considerations
- Network Delays: Network-related delays can contribute to the overall time it takes for links to be verified.
- Security Appliances: Email security appliances often perform link analysis, which can introduce noticeable delays.
- URL Rewriting: URL rewriting by security services adds an extra step in the process and can lead to delays.
Technical article
Documentation from Proofpoint shares that the Proofpoint TAP URL Defense rewrites URLs and analyzes them when clicked. There will therefore be a delay before the user is routed to their intended destination.
7 Jul 2024 - Proofpoint Documentation
Technical article
Documentation from Cisco explains that the Cisco Email Security Appliance will rewrite and follow the links contained in messages. There could be a small delay while it scans.
6 Mar 2025 - Cisco Documentation
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