What is the Google error message when an email exceeds size limits?

Key findings

• Specific error message: For emails exceeding Google's size limits, the common bounce message is 552-5.3.4 Your message exceeded Google's message size limits. This is often accompanied by a link to Google's support page for size guidelines.
• Gmail size limit: While attachments are commonly limited to 25 MB, Google's overall message size limit (as reported via SMTP) can be significantly higher, around 150 MB. This larger limit accounts for encoding overhead and the entire message content, not just attachments.
• Encoding overhead: Attachments and email content are often base64 encoded, which increases their size by approximately 33%. This means a 25 MB attachment could consume closer to 33 MB of the total message size limit.
• Automatic handling: For Gmail, if attachments exceed the 25 MB limit, they are often automatically uploaded to Google Drive, and a link to the file is embedded in the email instead of the file itself. This is a common workaround to avoid bounce messages.

Key considerations

• Monitor bounce messages: Regularly reviewing bounce logs and error messages is crucial for identifying size-related delivery issues. This proactive approach helps in maintaining a healthy sending reputation and ensures messages reach their intended recipients.
• Optimize content size: Beyond attachments, large HTML email bodies, excessive images, or inline CSS can also contribute to an email exceeding size limits. It's important to optimize overall email content, especially for marketing emails, to prevent clipping or delivery failures. For more on this, check out why Gmail may clip emails.
• Alternative sending methods: For sending large files, advise users to utilize cloud storage services like Google Drive, Dropbox, or OneDrive and share links instead of attaching files directly. This is a widely accepted practice for avoiding size restrictions.
• Educate clients: It is essential to educate clients and internal teams about email size limits and their implications for deliverability. This prevents misunderstandings, such as attributing size-related bounces to incorrect causes like mailbox over quota errors.

Key opinions

• Focus on engagement: Many marketers prioritize user engagement and visual appeal, sometimes leading to larger email sizes with high-resolution images or extensive HTML. They argue that a rich email experience is crucial for conversions.
• Attachment workarounds: There's a strong consensus that using cloud storage links for large files, rather than direct attachments, is the most practical solution. This is particularly true for documents, videos, or high-res images that would otherwise exceed typical 25 MB limits.
• Impact on campaigns: Marketers are concerned about bounce rates and undelivered messages due to size limits, as these directly affect campaign ROI. They seek ways to ensure their emails land in the inbox without triggering size-related blocklists or errors.
• Template optimization: A common approach is to design email templates that are lightweight, minimizing inline CSS and extraneous HTML, to keep the overall message size down and avoid max message size errors.

Key considerations

• Content delivery strategy: Instead of embedding large media, consider using engaging snippets with clear calls-to-action that link to a landing page where the full content or files are hosted. This also allows for better tracking.
• Image optimization: Compress images and use appropriate formats (e.g., WebP or optimized JPEGs) to reduce their file size without significant loss of quality. This is crucial for overall email weight.
• Testing email size: Marketers should regularly test their email campaigns to ensure they don't exceed common email size limits, which can be done with various email testing tools. Checking your email deliverability issues can prevent unexpected bounces.
• Client communication: It is important to clearly communicate the best practices for sending large files to clients, explaining that direct attachments can lead to bounces. This helps manage expectations and guides them towards more effective sharing methods. For example, TitanFile outlines several ways to send large files via Gmail.

Key opinions

• SMTP size declaration: Experts confirm that mailbox providers (like Google) declare their maximum accepted message size during the SMTP handshake via the EHLO command, specifically the SIZE extension. This provides the exact server-side limit.
• Distinction between content and attachment: It is important to differentiate between the maximum size for attachments (which is often smaller and more commonly known, like Gmail's 25 MB) and the overall maximum message size, which includes all headers, body text, and encoded attachments.
• Historical context: Some experts recall older anti-spam techniques, such as Hashcash, which aimed to combat spam by requiring senders to perform a small computational task. This shows how email security measures have evolved over time.
• Debugging tools: Tools like nc (netcat) or SWAKS are recommended for direct SMTP interaction to determine actual server limits and retrieve bounce messages precisely, aiding in troubleshooting deliverability issues.

Key considerations

• Proactive size checks: Before sending large campaigns, especially those with attachments or extensive HTML, it's wise to perform a size check against common recipient limits. This prevents unnecessary bounces and potential impact on sender reputation (or getting on a blocklist or blacklist, for example).
• Error code interpretation: Understanding SMTP error codes, such as 552 5.3.4 (message too large) or 556 (message too large), is fundamental for effective troubleshooting. This knowledge enables quick resolution of deliverability problems.
• Content optimization strategies: Experts advise on methods to reduce overall email size, including image compression, efficient HTML/CSS coding, and avoiding unnecessary padding or white space within the email's code. This improves both deliverability and loading times.
• Impact on deliverability: Regularly exceeding size limits can negatively affect a sender's reputation, as it signals a lack of adherence to recipient server policies. This can lead to increased spam filtering or even temporary blocks. Understanding why your emails fail is key to maintaining good sender health. Furthermore, knowing common message limits for different providers is essential.

Key findings

• Gmail's specific error: Google's support documentation confirms that if an email exceeds its size limits, users will receive a 552-5.3.4 error, stating that the message exceeded Google's message size limits.
• Attachment size vs. total message size: Documentation often distinguishes between the typical 25 MB limit for attachments and a larger overall message size limit (e.g., 150 MB for Gmail). The total message size includes all parts of the email after encoding.
• Automatic handling of large attachments: Many providers, including Gmail, automatically convert large attachments into shared links to cloud storage (like Google Drive) when the size limit is approached or exceeded, to facilitate delivery.
• SMTP size declaration: SMTP standards dictate that email servers announce their maximum acceptable message size using the SIZE extension during the EHLO handshake. This is the definitive technical limit.

Key considerations

• Adherence to guidelines: Senders should always consult and adhere to the published message size limits of major mailbox providers to ensure consistent deliverability. This is a fundamental aspect of maintaining good sender reputation.
• Encoding impact: It is crucial to factor in the size increase due to MIME encoding (e.g., base64), which can add approximately 33% to the original size of attachments and raw content. This often causes confusion if not accounted for.
• Use cloud storage for large files: Official documentation frequently recommends using cloud storage and sharing links for files exceeding typical attachment limits. This is presented as the most reliable method for transferring large files via email. Google's support page outlines their size guidelines.
• Comprehensive understanding: A thorough understanding of email file size limits as detailed in various documentation helps prevent bounce errors and ensures that email content is delivered as intended. This involves not only attachments but also the overall structure and content of the message.