async function handleBounce()

in packages/fxa-auth-server/lib/email/bounces.js [53:179]
85 lines of code
16 McCabe index (conditional complexity)

    async function handleBounce(message) {
      utils.logErrorIfHeadersAreWeirdOrMissing(log, message, 'bounce');

      let recipients = [];
      // According to the AWS SES docs, a notification will never
      // include multiple types, so it's fine for us to check for
      // EITHER bounce OR complaint here.
      if (message.bounce) {
        recipients = message.bounce.bouncedRecipients;
      } else if (message.complaint) {
        recipients = message.complaint.complainedRecipients;
      }

      // SES can now send custom headers if enabled on topic.
      // Headers are stored as an array of name/value pairs.
      // Log the `X-Template-Name` header to help track the email template that bounced.
      // Ref: http://docs.aws.amazon.com/ses/latest/DeveloperGuide/notification-contents.html
      const templateName = utils.getHeaderValue('X-Template-Name', message);
      const language = utils.getHeaderValue('Content-Language', message);

      for (const recipient of recipients) {
        // The email address in the bounce message has been handled by an external
        // system, and depending on the system it can have had some strange things
        // done to it.  Try to normalize as best we can.
        let email;
        let emailIsValid = true;
        const parsedAddress = eaddrs.parseOneAddress(recipient.emailAddress);
        if (parsedAddress !== null) {
          email = parsedAddress.address;
        } else {
          email = recipient.emailAddress;
          if (!isValidEmailAddress(email)) {
            emailIsValid = false;
            // We couldn't make the recipient address look like a valid email.
            // Log a warning but don't error out because we still want to
            // emit flow metrics etc.
            log.warn('handleBounce.addressParseFailure', {
              email: email,
              action: recipient.action,
              diagnosticCode: recipient.diagnosticCode,
            });
          }
        }
        const emailDomain = utils.getAnonymizedEmailDomain(email);
        const logData = {
          action: recipient.action,
          email: email,
          domain: emailDomain,
          bounce: !!message.bounce,
          diagnosticCode: recipient.diagnosticCode,
          mailStatus: recipient.status,
        };
        const bounce = {
          email: email,
          diagnosticCode: recipient.diagnosticCode,
        };

        // Template name corresponds directly with the email template that was used
        if (templateName) {
          logData.template = templateName;
          bounce.templateName = templateName;
        }

        if (language) {
          logData.lang = language;
        }

        // Log the type of bounce that occurred
        // Ref: http://docs.aws.amazon.com/ses/latest/DeveloperGuide/notification-contents.html#bounce-types
        if (message.bounce && message.bounce.bounceType) {
          bounce.bounceType = logData.bounceType = message.bounce.bounceType;

          if (message.bounce.bounceSubType) {
            bounce.bounceSubType = logData.bounceSubType =
              message.bounce.bounceSubType;
          }
        } else if (message.complaint) {
          // Log the type of complaint and userAgent reported
          logData.complaint = !!message.complaint;
          bounce.bounceType = 'Complaint';

          if (message.complaint.userAgent) {
            logData.complaintUserAgent = message.complaint.userAgent;
          }

          if (message.complaint.complaintFeedbackType) {
            bounce.bounceSubType = logData.complaintFeedbackType =
              message.complaint.complaintFeedbackType;
          }
        }

        // Log the bounced flowEvent and emailEvent metrics
        utils.logFlowEventFromMessage(log, message, 'bounced');
        utils.logEmailEventFromMessage(log, message, 'bounced', emailDomain);
        utils.logAccountEventFromMessage(message, 'emailBounced');

        log.info('handleBounce', logData);

        /**
         * Docs: https://docs.aws.amazon.com/ses/latest/DeveloperGuide/notification-contents.html#bounce-types
         * Bug: https://github.com/mozilla/fxa-content-server/issues/5629
         *
         * If there is any type of bounce then suggest account for deletion.
         * Code below will fetch the email record and if it is an unverified new account then it will delete
         * the account.
         */
        const suggestAccountDeletion = !!bounce.bounceType;
        const work = [];

        if (emailIsValid) {
          work.push(recordBounce(bounce).catch(gotError.bind(null, email)));
          if (suggestAccountDeletion) {
            work.push(
              findEmailRecord(email).then(
                deleteAccountIfUnverifiedNew,
                gotError.bind(null, email)
              )
            );
          }
        }

        await Promise.all(work);
      }

      // We always delete the message, even if handling some addrs failed.
      message.del();
    }