Enum Error 

#[non_exhaustive]
pub enum Error {
    Io(Arc<Error>),
    Auth {
        message: String,
        response: SmtpResponse,
    },
    Permanent {
        code: u16,
        message: String,
        response: SmtpResponse,
    },
    Transient {
        code: u16,
        message: String,
        response: SmtpResponse,
    },
    Protocol(String),
    Parse(String),
    Timeout,
    Closed,
    StartTlsUnavailable,
    AllRecipientsFailed {
        count: usize,
        responses: Vec<SmtpResponse>,
    },
    SmtpUtf8Required,
}

Error type for SMTP client operations.

Implements Serialize/Deserialize behind the serde feature flag. The Io variant is serialized as its ErrorKind name and message string; on deserialization an std::io::Error is reconstructed from these fields.

Variants (Non-exhaustive)

Non-exhaustive enums could have additional variants added in future. Therefore, when matching against variants of non-exhaustive enums, an extra wildcard arm must be added to account for any future variants.

Io(Arc<Error>)

Underlying I/O error (includes TLS transport errors).

Wrapped in Arc so that Error can implement Clone.

Auth

Authentication was rejected by the server (RFC 4954 Section 4).

The response field preserves the full server reply so callers can distinguish transient failures (454) from permanent ones (535).

Fields

message: String

response: SmtpResponse

Permanent

Permanent failure — 5xx response (RFC 5321 Section 4.2.1). Do not retry.

Fields

code: u16

message: String

response: SmtpResponse

Transient

Transient failure — 4xx response (RFC 5321 Section 4.2.1). May succeed on retry.

Fields

code: u16

message: String

response: SmtpResponse

Protocol(String)

SMTP protocol violation by the server (RFC 5321 Section 4.2).

Parse(String)

Failed to parse a server response (RFC 5321 Section 4.2).

Timeout

Operation exceeded the caller-supplied timeout (RFC 5321 Section 4.5.3.2).

Closed

The connection has been closed (RFC 5321 Section 3.8).

StartTlsUnavailable

STARTTLS was requested but the server does not advertise it (RFC 3207).

AllRecipientsFailed

All recipients were rejected (RFC 5321 Section 3.3 / RFC 1854 Section 3).

Fields

count: usize

responses: Vec<SmtpResponse>

SmtpUtf8Required

The message or envelope requires SMTPUTF8, but the server does not advertise the SMTPUTF8 extension (RFC 6531 Sections 3.1, 3.3, 3.4).

Implementations

impl Error

pub fn is_transient(&self) -> bool

Returns true if the error is transient and the operation may succeed on retry.

Transient errors include 4xx SMTP responses (RFC 5321 Section 4.2.1), I/O errors, timeouts, and transient auth failures (454, RFC 4954 Section 4).

pub fn is_permanent(&self) -> bool

Returns true if the error is permanent and the operation should not be retried.

Permanent errors include 5xx SMTP responses (RFC 5321 Section 4.2.1) and permanent authentication failures (535, RFC 4954 Section 4).

Trait Implementations

impl Clone for Error

fn clone(&self) -> Error

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for Error

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Display for Error

fn fmt(&self, __formatter: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Error for Error

fn source(&self) -> Option<&(dyn Error + 'static)>

Returns the lower-level source of this error, if any.

fn description(&self) -> &str

👎Deprecated since 1.42.0:

use the Display impl or to_string()

fn cause(&self) -> Option<&dyn Error>

👎Deprecated since 1.33.0:

replaced by Error::source, which can support downcasting

fn provide<'a>(&'a self, request: &mut Request<'a>)

🔬This is a nightly-only experimental API. (error_generic_member_access)

Provides type-based access to context intended for error reports.

impl From<Error> for Error

fn from(e: Error) -> Self

Converts to this type from the input type.

impl From<ValidationError> for Error

fn from(e: ValidationError) -> Self

Converts to this type from the input type.

impl PartialEq for Error

Compares two SMTP errors for equality.

The Io variant compares by std::io::ErrorKind only, since std::io::Error does not implement PartialEq. Two Io errors with the same ErrorKind are considered equal even if their messages differ.

fn eq(&self, other: &Self) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl Eq for Error