Gmail flags outbound links due to a combination of factors relating to the linked website's reputation, content, and security, as well as the sender's email practices and authentication. These include the domain being on a Google Safe Browsing blacklist, having a low reputation (especially for new domains), containing low-quality or spammy content, a high rate of user-reported spam, malware or phishing activity, and issues with email authentication (SPF, DKIM, DMARC). Poor list hygiene (spam traps, unengaged subscribers), a bad IP reputation, link cloaking, or unusual strings in the URL can also contribute to the problem. Resolving this requires improving domain reputation, ensuring website security, cleaning email lists, setting up proper authentication, monitoring IP reputation, and avoiding deceptive linking practices.
13 marketer opinions
Gmail flags outbound links due to various factors related to the link's destination, the sender's reputation, and email content/configuration. Issues range from the linked domain's reputation, presence on blacklists, or association with spam/malware, to problems with the sender's email authentication, IP reputation, or list hygiene. Resolving the issue involves addressing these potential problems through domain warming, content review, link validation, email authentication setup, and list cleaning.
Marketer view
Marketer from Email Geeks suggests that if the blog allows comments, a spam or phishing link in the comments could be causing the issue.
20 Nov 2023 - Email Geeks
Marketer view
Email marketer from Stack Overflow explains that Gmail might flag links if the domain lacks a strong reputation. Establishing domain authority through consistent, positive engagement and ensuring the domain isn't associated with spam can help.
22 Dec 2023 - Stack Overflow
2 expert opinions
Gmail may flag outbound links due to the linked domain's reputation, particularly if it's new or associated with low-quality content. Additionally, techniques like link cloaking, where the displayed URL differs from the destination, can trigger flagging. Resolving this involves building a positive domain reputation through consistent sending practices and ensuring transparent, direct linking.
Expert view
Expert from Word to the Wise explains that Gmail may be flagging links due to the domain's reputation, especially if the domain is new or has a history of sending low-quality content. Building a good sending reputation takes time and consistency.
1 Nov 2024 - Word to the Wise
Expert view
Expert from Spam Resource responds that Gmail may flag links if it detects techniques such as link cloaking (where the displayed URL is different from the actual destination). Ensure transparency by using clear and direct links.
26 Dec 2023 - Spam Resource
3 technical articles
Gmail flags outbound links due to a high spam rate reported by users, the detection of malware or phishing on the linked website, or incorrect DNS records (SPF, DKIM, DMARC). These factors negatively impact sender reputation and user safety.
Technical article
Documentation from Google Search Central indicates that if Google detects malware or phishing activity on the linked website, Gmail will flag the links to protect users, regardless of the sender's reputation.
31 Mar 2025 - Google
Technical article
Documentation from Google Postmaster Tools explains that a high spam rate reported by users for emails from a domain can negatively impact the reputation of links included in those emails, leading to flagging.
7 May 2022 - Google
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