Summary
Gmail deletes href tags on zip download links for a multitude of reasons primarily related to security and spam prevention. Gmail employs security measures to prevent malicious content, including malware and XSS attacks, leading to the removal or modification of links to executable files or archives like zip files. Aggressive spam filtering algorithms identify zip files as potential threats, stripping links even if the files are harmless. Gmail also rewrites links for tracking, potentially interfering with zip download links. Furthermore, domain reputation, link caching, incorrect MIME types, and improperly configured Content-Disposition headers can all contribute to the issue. HTML rendering inconsistencies across email clients can trigger spam filters, leading to link removal as well.
Key findings
- Security & Spam: Gmail's primary concern is protecting users from malicious content and phishing attacks, resulting in aggressive spam filtering.
- Domain Reputation: Gmail considers the reputation of the domain hosting the zip file; a low reputation increases the likelihood of link removal.
- Link Rewriting & Caching: Gmail rewrites and caches links, and can globally update them if malicious activity is detected, impacting zip file links.
- Technical Factors: Incorrect MIME types, improperly configured Content-Disposition headers, and HTML rendering inconsistencies can trigger Gmail's filters.
- Workspace vs. Free Gmail: Google Workspace and free Gmail accounts may handle zip file links differently, with stricter policies in place for Workspace.
Key considerations
- Scan Zip Files: Scan zip files with multiple antivirus tools and host them on reputable platforms.
- Use Reputable Hosting: Use reputable hosting providers to avoid being flagged as suspicious.
- Check MIME Types & Headers: Ensure correct MIME types and properly configure the Content-Disposition header.
- Test Different Sending Methods: Experiment with different sending methods (GWS, API) to see if one bypasses Gmail's filters.
- Consider Alternatives: Consider alternative methods for sharing files, such as cloud storage services, if zip files consistently face deliverability issues.
What email marketers say
10 marketer opinions
Gmail may delete href tags on zip download links due to a combination of factors, including security concerns, spam filtering, and link rewriting. Gmail's security measures aim to protect users from malicious content and phishing threats, leading to aggressive spam filtering that can flag links to downloadable files, especially zips. Link rewriting for tracking purposes can also interfere with specific link types. Additionally, Gmail's link caching and domain reputation assessments play a role, as low-reputation domains and previously flagged links can be globally updated or stripped. HTML rendering inconsistencies and incorrect MIME types can further contribute to the issue.
Key opinions
- Security Measures: Gmail's security measures actively prevent malicious content by removing or modifying links to executable files or archives like zip files.
- Aggressive Spam Filtering: Gmail's aggressive spam filtering algorithms can flag emails with links to downloadable files as potentially harmful, leading to link removal.
- Link Rewriting: Gmail rewrites links for tracking, which may interfere with specific link types, including zip download links.
- Domain Reputation: Gmail evaluates the reputation of the domain hosting the zip file; a low reputation may result in the link being stripped.
- Link Caching: Gmail caches links and globally updates them if a cached link is flagged as malicious, potentially removing the href attribute from links deemed unsafe.
Key considerations
- Test File Hosting: Consider using different file hosting and link shortening services to see if it resolves the issue.
- Scan Zip Files: Scan zip files with multiple antivirus tools to ensure they are clean and free of malware before linking to them.
- Reputable Platforms: Host zip files on reputable platforms to increase trust and reduce the likelihood of Gmail flagging the links.
- Domain Reputation: Ensure your sending domain has a good reputation to avoid being flagged as suspicious.
- Content-Disposition Header: If using a 'Content-Disposition' header, ensure it's correctly configured to avoid triggering spam filters.
- MIME Types: Verify that the MIME type for the zip file is correctly specified to prevent misinterpretation by Gmail.
Marketer view
Email marketer from SendPulse shares that Gmail's aggressive spam filtering can sometimes flag emails with links to downloadable files. The algorithm might perceive them as potentially harmful and remove the link.
1 Jun 2024 - SendPulse
Marketer view
Email marketer from MarketingProfs explains that HTML rendering inconsistencies across email clients can cause issues. Gmail might strip links if they are formatted in a way that triggers its spam or security filters.
10 Feb 2024 - MarketingProfs
What the experts say
2 expert opinions
Experiences with Gmail and zip file links vary. One expert successfully sent zip file links via GWS and their Email API, while another highlights Gmail's tendency to block zip files due to potential malware concerns, even if harmless.
Key opinions
- Successful Delivery: Zip file links can sometimes be successfully delivered through Gmail, particularly using GWS and reputable Email APIs.
- Aggressive Blocking: Gmail often blocks zip file links as a precautionary measure due to their association with malware.
Key considerations
- Test Sending Methods: Experiment with different sending methods (GWS, API) to see if some bypass Gmail's filters.
- Reputation Matters: Maintain a good sending reputation to decrease the likelihood of being flagged.
- Explore Alternatives: Consider alternative file sharing methods if zip files consistently face deliverability issues.
Expert view
Expert from Word to the Wise explains that Gmail often blocks zipped attachments or links to zipped files due to their potential for containing malware. Even if the zip itself is harmless, the presence of a zip can trigger aggressive spam filtering.
25 Aug 2024 - Word to the Wise
Expert view
Expert from Email Geeks shares that they are able to send a link to a remotely hosted zip file from a GWS account to a regular Gmail account without any issues. They also mention sending it from their Email API to Gmail, Yahoo, and WebDE successfully.
19 Jul 2021 - Email Geeks
What the documentation says
5 technical articles
Gmail removes href tags on zip download links primarily due to security concerns, including preventing malicious content, XSS attacks, and potential harm from improperly configured headers. Gmail sanitizes HTML, scrutinizes unusual link attributes, and may remove links if the Content-Disposition header suggests direct download or if MIME types are incorrect, all to protect users.
Key findings
- Security Measures: Gmail employs security measures to prevent malicious content by removing or modifying links to executable files and archives like zip files.
- XSS Prevention: Gmail sanitizes HTML code to prevent Cross-Site Scripting (XSS) attacks, potentially stripping links with harmful attributes, especially if the domain is untrusted.
- Content-Disposition Issues: If the Content-Disposition header suggests direct download, Gmail may scrutinize or remove the link as a precaution.
- MIME Type Errors: Incorrectly specified MIME types can cause Gmail to misinterpret the file type, leading to link removal.
Key considerations
- Ensure Clean Code: Write clean and standard HTML to minimize potential triggers for Gmail's HTML sanitization processes.
- Proper Headers: Properly configure the Content-Disposition header to avoid issues related to direct downloads.
- Correct MIME Types: Specify correct MIME types for the zip file to ensure Gmail accurately interprets the file.
- Trustworthy Domains: Host files on trustworthy domains to reduce the chance of links being flagged as suspicious.
Technical article
Documentation from Stack Overflow explains that Gmail sanitizes HTML code to prevent XSS attacks. Links with unusual or potentially harmful attributes can be stripped, including those directing to downloadable files, especially if the domain is untrusted.
4 Dec 2021 - Stack Overflow
Technical article
Documentation from OWASP explains that Gmail is designed to prevent Cross-Site Scripting (XSS) attacks. By removing certain attributes from links, Gmail ensures that malicious scripts cannot be executed through email content, which can affect download links.
7 Oct 2021 - OWASP
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