"SMTPSENT.BareLineFeedsAreIllegal" NDR received by Exchange Online or EOP users in Office 365 Dedicated/ITAR
Supporting Microsoft Article: https://support.microsoft.com/en-gb/kb/2998901
SMTPSEND.BareLinefeedsAreIllegal; message contains bare linefeeds, which cannot be sent via DATA
- Request that the sender correct the message format. This error frequently occurs with automated mailers (for example, reports or invoices) and bulk senders.
- Enable Extended SMTP (ESMTP) on the receiving server so that the message can be sent by using CHUNKING or the BDAT command. Neither of these methods depends on the CR-LF combination to signal the end of the message. For more information, see SMTP protocol extensions.
- If the sender cannot correct the sent messages, or if the gap must be bridged until the message format is corrected, the recipient can create an inbound transport rule to append a disclaimer to the messages from the problematic sender. The disclaimer will append the expected CR-LF combination to the message so that it can be delivered. (This disclaimer may consist of a single character such as a period or a dash.)
For more info about how to create disclaimers, see Organization-wide disclaimers, signatures, footers, or headers.