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ContentTransferEncoding

property ContentTransferEncoding: string read write;

Example​

procedure ConfigureQuotedPrintableBody;
var
  Msg: TIdMessage;
begin
  Msg := Email;
  if Msg = nil then Exit;

  Msg.Encoding := mePlainText;
  Msg.ContentType := 'text/plain';
  Msg.CharSet := 'utf-8';
  Msg.ContentTransferEncoding := 'quoted-printable';
end;

Usage​

ContentTransferEncoding selects or reports the message-level transfer label, with base64/quoted-printable body encoding and part-related normalization performed only later.

Additional Technical Info​

ContentTransferEncoding is the message-level transfer-encoding value parsed from or generated into Content-Transfer-Encoding. Assignment stores the String verbatim. Validation and actual encoding are deferred until generation/body output.

For a non-single-part message with no MessageParts, values whose first header token is base64 or quoted-printable make normal full output encode the entire Body using the current CharSet. Other values normally leave Body on the line-writing path while still labeling the header, so an unsupported/mismatched value can create invalid or misleading output.

Interaction with parts and layout​

GenerateHeader recounts parts. If at least one exists and this property is nonempty but not 7bit, 8bit or binary, it clears the property permanently because Indy cannot wrap a multipart body in base64/quoted-printable. Individual parts keep their own ContentTransfer values and are encoded separately.

For calculated single-part MIME, the message-level generated header is removed and the one part supplies its transfer header. For other MIME and plain layouts, the surviving typed value is projected into the message header.

ProcessHeaders copies the raw value into this field. Receive logic recognizes standard values, applies MIME restrictions, and can fall back to treating unknown transfer types as 8-bit/application data. It may decode content into Body or MessageParts, so the typed label is not evidence that Body still contains encoded wire text; NoDecode is the explicit bypass.

NoEncode ignores this property and writes raw Headers/Body. The example is source-reviewed only; no encoder ran.

External references

Created 2026-07-15