Why are email attachments being lost when sending from Java API to G Suite accounts?
Summary
What email marketers say10Marketer opinions
Email marketer from SMTPFix Blog explains that some content filters might be triggered by the attachment's file type or content. They may automatically remove attachments that match specific criteria, especially if the content looks like spam.
Email marketer from Java Forums points out that encoding issues can sometimes cause attachments to be lost or corrupted. Ensure that the attachment content is properly encoded (e.g., using Base64) before adding it to the email.
Email marketer from Mailtrap Blog suggests checking the sender's reputation and ensuring that the sending domain is properly authenticated (SPF, DKIM, DMARC). Poor sender reputation can cause emails to be filtered or modified.
Email marketer from StackExchange mentions that G Suite can be sensitive to filename extensions. Ensure the extensions are correctly set and safe. Changing filename extensions can prevent some filters from blocking the attachment.
Email marketer from Reddit mentions that G Suite has file size limits for attachments. Check if the combined size of your email and attachments exceeds these limits. Large attachments can be rejected or stripped.
Email marketer from Email Marketing Forum suggests that some antivirus software or email security filters on the recipient's end might be stripping attachments if they are deemed suspicious. Suggests informing recipients to check their spam/quarantine folders.
Email marketer from Stack Overflow explains that the issue might be due to incorrect MIME type settings. Suggests ensuring the correct MIME type is set when creating the `MimeBodyPart` for the attachment. For example, for PDF, use `application/pdf`.
Email marketer from Email Deliverability Forum suggests sending test emails with various types and sizes of attachments to identify if a specific type is causing the issue. This helps isolate the problem.
Marketer from Email Geeks mentions that G Suite customers can divert inbound emails to another destination with additional filtering, and suggests confirming that attachments are actually being sent to all recipients and that the mail code is working as intended.
Email marketer from TechTarget explains that using TLS encryption during email transmission can prevent tampering with email content, which includes attachments. Lack of encryption may lead to unexpected modifications.
What the experts say5Expert opinions
Expert from Word to the Wise explains that G Suite and other email providers perform deep content scanning of attachments. If the attachment's content triggers a spam filter (even if it's not actually spam), the attachment might be removed or the entire email blocked.
Expert from Spam Resource emphasizes that sender reputation heavily influences attachment delivery. If your sending IP or domain has a poor reputation, G Suite is more likely to scrutinize and potentially strip attachments, especially from unfamiliar senders.
Expert from Email Geeks says that whitelisting at Google is not possible, but individual users might be able to whitelist the sender. Recommends having someone check the generated files for anything that might make them look malicious.
Expert from Email Geeks states that Gmail typically delivers attachments without issues, so the problem likely stems from something suspicious within the attachments themselves.
Expert from Email Geeks suggests inbox settings as a possible cause and says G Suite does not strip attachments, but individual domains might if attachments seem 'iffy' or unknown.
What the documentation says5Technical articles
Documentation from OWASP suggests that when file attachments are involved, security checks need to be performed to prevent malicious content. This includes checking file types, sizes, and contents for known threats.
Documentation from RFC Editor describes the standards for MIME (Multipurpose Internet Mail Extensions). This document explains how to properly format email messages with attachments, including setting content types, encoding, and boundaries.
Documentation from Apache Commons suggests that correctly handling file uploads (if applicable) is essential to ensure the integrity of attachments. Correctly read and represent the data from the file.
Documentation from Oracle provides information on using the JavaMail API correctly. It emphasizes the importance of setting the correct content type and disposition for attachments using the `setContent` and `setDisposition` methods.
Documentation from Google Workspace Admin Help explains that Gmail has a maximum attachment size limit of 25 MB. If your attachments exceed this limit, they may be stripped or the email may not be delivered.