There are a number of reasons why you may see the "This message was blocked because its content presents a potential security issue" error in Gmail. Gmail blocks messages that may spread viruses, like messages that include executable files or certain links.
Why messages get blocked
To protect you against potential viruses and harmful software, Gmail doesn't allow you to attach certain types of files, including:
- Certain types of files, including their compressed form (like .gz or .bz2 files) or when found within archives (like .zip or .tgz files)
- Documents with malicious macros
- Password protected archives whose content is an archive
Note: If you try to attach a document that is too large, your message won't send. Learn more about attachments and file size limits.
Types you can't include as attachments
To protect your account, Gmail doesn't allow you to attach certain types of files. Gmail often updates the types of files not allowed to keep up with harmful software that is constantly changing. Some examples include:
.ade, .adp, .apk, .appx, .appxbundle, .bat, .cab, .chm, .cmd, .com, .cpl, .dll, .dmg, .exe, .hta, .ins, .isp, .iso, .jar, .js, .jse, .lib, .lnk, .mde, .msc, .msi, .msix, .msixbundle, .msp, .mst, .nsh, .pif, .ps1, .scr, .sct, .shb, .sys, .vb, .vbe, .vbs, .vxd, .wsc, .wsf, .wsh
What you can do
If you're sure the file is safe, you can ask the sender to upload the file to Google Drive. Then send it as a Drive attachment.
Sometimes messages are blocked when you don't include any attachments.
This can happen when you include content, images, or links that might share viruses.