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IsMsgSinglePartMime

property IsMsgSinglePartMime: Boolean read write;

Example​

procedure InspectGeneratedLayout(var Value: Variant);
var
  Msg: TIdMessage;
begin
  Msg := Email;
  if Msg = nil then Exit;

  Msg.GenerateHeader;
  Value := Msg.IsMsgSinglePartMime;
end;

Usage​

IsMsgSinglePartMime exposes derived single-entity processing state that generation and receive logic overwrite, including encoded plain-text bodies despite the property name.

Additional Technical Info​

IsMsgSinglePartMime is internal layout/decoder state exposed as a writable Boolean. Treat it as derived and observational rather than configuration.

GenerateHeader overwrites it with True only when Encoding is meMIME, MessageParts has exactly one item, and Body is empty under Indy's whitespace-only test. Normal send/save calls GenerateHeader immediately before body output, so a script's earlier manual assignment is discarded.

When true during output, Indy does not emit the normal message/body separator and multipart boundary framing. It removes message-level content headers from the generated set and lets the one part append its headers/content directly.

Receive logic overloads the flag more broadly. It sets it true for the decoder branch handling single-part MIME or a mePlainText body whose message-level transfer encoding is base64/quoted-printable. A decoded text entity can be placed in message Body; an attachment can be created as a part. Thus True after loading does not prove Encoding = meMIME or MessageParts.Count = 1.

ClearHeader resets the flag false. NoDecode avoids the decoder branch, and NoEncode bypasses generation/body layout and does not use it. Direct writes can only influence native paths that consume state without first recalculating it; those paths are not exposed as a safe script contract.

Calling GenerateHeader solely to inspect the value also mutates many other message fields, including Encoding, boundaries, headers and some part/address state. The example is illustrative and source-reviewed; it was not executed.

External references

Created 2026-07-15