/**
 * Constants for the easy-email library
 */
export declare const EMAIL_CONSTANTS: {
    readonly VALIDATION_MESSAGES: {
        readonly SENDER_REQUIRED: "Sender email is required";
        readonly RECIPIENT_REQUIRED: "Recipient is required";
        readonly SUBJECT_REQUIRED: "Subject is required";
        readonly NO_PROVIDER_CONFIGURED: "No email provider configured";
        readonly SMTP_NOT_CONFIGURED: "SMTP transporter not configured";
        readonly SES_REGION_REQUIRED: "SES region is required";
        readonly SES_CREDENTIALS_REQUIRED: "SES credentials are required";
    };
    readonly ERROR_CODES: {
        readonly VALIDATION_ERROR: "VALIDATION_ERROR";
        readonly CONFIG_ERROR: "CONFIG_ERROR";
        readonly PROVIDER_ERROR: "PROVIDER_ERROR";
        readonly CONNECTION_FAILED: "CONNECTION_FAILED";
        readonly SES_ERROR: "SES_ERROR";
    };
    readonly PROVIDER_TYPES: {
        readonly SMTP: "smtp";
        readonly SENDGRID: "sendgrid";
        readonly SES: "ses";
    };
    readonly TEMPLATE: {
        readonly VARIABLE_REGEX: RegExp;
        readonly DEFAULT_EXTENSION: ".html";
    };
    readonly CONTENT_TYPES: {
        readonly TEXT_PLAIN: "text/plain";
        readonly TEXT_HTML: "text/html";
    };
    readonly DEFAULTS: {
        readonly FROM_NAME: "";
        readonly ATTACHMENT_DISPOSITION: "attachment";
    };
    readonly LOG_MESSAGES: {
        readonly EMAIL_SENT: "Email sent successfully";
        readonly EMAIL_FAILED: "Failed to send email";
        readonly CONNECTION_VERIFIED: "Connection verified successfully";
        readonly CONNECTION_FAILED: "Connection verification failed";
    };
};
export declare const OBSERVABILITY_CONSTANTS: {
    readonly EVENT_TYPES: {
        readonly EMAIL_SENT: "email_sent";
        readonly EMAIL_FAILED: "email_failed";
        readonly CONNECTION_VERIFIED: "connection_verified";
        readonly CONNECTION_FAILED: "connection_failed";
    };
    readonly PROVIDER_NAMES: {
        readonly SMTP: "smtp";
        readonly SENDGRID: "sendgrid";
        readonly SES: "ses";
    };
    readonly METRICS_KEYS: {
        readonly TOTAL_SENT: "totalSent";
        readonly TOTAL_FAILED: "totalFailed";
        readonly SUCCESS_RATE: "successRate";
        readonly AVERAGE_SEND_TIME: "averageSendTime";
    };
};
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