RFC2183 is an Attachment Filtering option within Reflexion Total Control. If a message is tagged with the error message provided in your quarantine, this means that the message sent to or from you does not meet the standards listed out by the IETF.
What is RFC2183?
RFC2183 is an IETF memo for how to handle files transferred through email (aka, attachments). The memo outlines standard and guidelines for how to handle these files, and how they should be encoded into the headers of the message.
This does provide a number of limitation in how messages are handled, including, but not limited, to:
Files created within a mail client instead of on a filesystem (read receipts, msg/eml files, e-contact cards)
Filenames that are not created within US-ASCII standards (no characters with tilde or umlaut)
Executable style files that are embedded directly into the message
For more information directly from the IETF, please visit the the below website: