Error sending notification email about mgob HOT 5 CLOSED

docker-compose.yml
version: "3.8"
services:
  my-cloud-backup-manager:
    restart: always
    image: maxisam/mgob:latest
    networks:
      - my-cloud-backup-manager-network
      - my-cloud-backup-network
      - my-cloud-proxy-network
    ports:
      - "8090"
    volumes:
      - ./my-cloud-backup-files/config:/config
      - ./my-cloud-backup-files/storage:/storage
      - ./my-cloud-backup-files/tmp:/tmp
      - ./my-cloud-backup-files/data:/data
      - ./my-cloud-backup-files/keys:/secret

networks:
  my-cloud-backup-manager-network:
    driver: bridge
  my-cloud-backup-network:
    name: my-cloud-backup-network
  my-cloud-proxy-network:
    name: my-cloud-proxy-network

scheduler:
  # run every day at 6:00 and 18:00 UTC
  cron: "0 3 * * *"
  # number of backups to keep locally
  retention: 10
  # backup operation timeout in minutes
  timeout: 720
target:
  # mongod IP or host name
  host: "my-cloud-mongodb-prod"
  # mongodb port
  port: 27017
  # mongodb database name, leave blank to backup all databases
  database: "my-cloud"
  # leave blank if auth is not enabled
  username: "root"
  password: "my-cloud-passwd"
  # add custom params to mongodump (eg. Auth or SSL support), leave blank if not needed
  #params: "--ssl --authenticationDatabase admin"
#retry:
  # number of retries
#  attempts: 3
  # backoff factor  * (2 ^ attemptCount) seconds
#  backoffFactor: 60
encryption:
  gpg:
    keyFile: /secret/key-gpg.pub
sftp:
  host: my-cloud.myhost
  port: 7586
  username: my-user-name
  password: my-passwd
  # you can also specify path to a private key and a passphrase
  # dir must exist on the SFTP server
  dir: company/my-cloud
smtp:
  server: smtp.kinghost.net
  port: 587
  username: [email protected]
  password: my-passwd-backup
  from: [email protected]
  to:
    - [email protected]
    - [email protected]
  # 'true' to notify only on failures
  warnOnly: false