# `email.errors`: Exception and Defect classes

Source code: Lib/email/errors.py

The following exception classes are defined in the `email.errors` module:

exception email.errors.MessageError

  This is the base class for all exceptions that the `email` package can raise. It is derived from the standard `Exception` class and defines no additional methods.

exception email.errors.MessageParseError

  This is the base class for exceptions raised by the `Parser` class. It is derived from `MessageError`. This class is also used internally by the parser used by `headerregistry`.

exception email.errors.HeaderParseError

  Raised under some error conditions when parsing the RFC 5322 headers of a message, this class is derived from `MessageParseError`. The `set_boundary()` method will raise this error if the content type is unknown when the method is called. `Header` may raise this error for certain base64 decoding errors, and when an attempt is made to create a header that appears to contain an embedded header (that is, there is what is supposed to be a continuation line that has no leading whitespace and looks like a header).

exception email.errors.BoundaryError

  Deprecated and no longer used.

exception email.errors.MultipartConversionError

  Raised if the `attach()` method is called on an instance of a class derived from `MIMENonMultipart` (e.g. `MIMEImage`). `MultipartConversionError` multiply inherits from `MessageError` and the built-in `TypeError`.

exception email.errors.HeaderWriteError

  Raised when an error occurs when the `generator` outputs headers.

exception email.errors.MessageDefect

  This is the base class for all defects found when parsing email messages. It is derived from `ValueError`.

exception email.errors.HeaderDefect

  This is the base class for all defects found when parsing email headers. It is derived from `MessageDefect`.

Here is the list of the defects that the `FeedParser` can find while parsing messages. Note that the defects are added to the message where the problem was found, so for example, if a message nested inside a multipart/alternative had a malformed header, that nested message object would have a defect, but the containing messages would not.

All defect classes are subclassed from `email.errors.MessageDefect`.

exception email.errors.NoBoundaryInMultipartDefect

  A message claimed to be a multipart, but had no boundary parameter.

exception email.errors.StartBoundaryNotFoundDefect

  The start boundary claimed in the Content-Type header was never found.

exception email.errors.CloseBoundaryNotFoundDefect

  A start boundary was found, but no corresponding close boundary was ever found.

  Added in version 3.3.

exception email.errors.FirstHeaderLineIsContinuationDefect

  The message had a continuation line as its first header line.

exception email.errors.MisplacedEnvelopeHeaderDefect

  A “Unix From” header was found in the middle of a header block.

exception email.errors.MissingHeaderBodySeparatorDefect

  A line was found while parsing headers that had no leading white space but contained no ‘:’. Parsing continues assuming that the line represents the first line of the body.

  Added in version 3.3.

exception email.errors.MalformedHeaderDefect

  A header was found that was missing a colon, or was otherwise malformed.

  Deprecated since version 3.3: This defect has not been used for several Python versions.

exception email.errors.MultipartInvariantViolationDefect

  A message claimed to be a multipart, but no subparts were found. Note that when a message has this defect, its `is_multipart()` method may return `False` even though its content type claims to be multipart.

exception email.errors.InvalidBase64PaddingDefect

  When decoding a block of base64 encoded bytes, the padding was not correct. Enough padding is added to perform the decode, but the resulting decoded bytes may be invalid.

exception email.errors.InvalidBase64CharactersDefect

  When decoding a block of base64 encoded bytes, characters outside the base64 alphabet were encountered. The characters are ignored, but the resulting decoded bytes may be invalid.

exception email.errors.InvalidBase64LengthDefect

  When decoding a block of base64 encoded bytes, the number of non-padding base64 characters was invalid (1 more than a multiple of 4). The encoded block was kept as-is.

exception email.errors.InvalidDateDefect

  When decoding an invalid or unparsable date field. The original value is kept as-is.