Thanks for the reply.
I will display the results first.
stdout:
Feb 06 16:20:31 ITS-ELST-01 logstash[689501]: {
Feb 06 16:20:31 ITS-ELST-01 logstash[689501]:      "timestamp" => "Feb  6 16:20:24",
Feb 06 16:20:31 ITS-ELST-01 logstash[689501]:          "agent" => {
Feb 06 16:20:31 ITS-ELST-01 logstash[689501]:              "version" => "7.12.1",
Feb 06 16:20:31 ITS-ELST-01 logstash[689501]:                 "name" => "MY-SERVER",
Feb 06 16:20:31 ITS-ELST-01 logstash[689501]:             "hostname" => "MY-SERVER",
Feb 06 16:20:31 ITS-ELST-01 logstash[689501]:         "ephemeral_id" => "d4d40b29-a2d6-477d-b275-ce3c6bb2be1a",
Feb 06 16:20:31 ITS-ELST-01 logstash[689501]:                   "id" => "87215304-c7a1-4914-b057-ef6a368959eb",
Feb 06 16:20:31 ITS-ELST-01 logstash[689501]:                 "type" => "filebeat"
Feb 06 16:20:31 ITS-ELST-01 logstash[689501]:     },
Feb 06 16:20:31 ITS-ELST-01 logstash[689501]:     "@timestamp" => 2024-02-06T07:20:30.758Z,
Feb 06 16:20:31 ITS-ELST-01 logstash[689501]:            "ecs" => {
Feb 06 16:20:31 ITS-ELST-01 logstash[689501]:         "version" => "1.8.0"
Feb 06 16:20:31 ITS-ELST-01 logstash[689501]:     },
Feb 06 16:20:31 ITS-ELST-01 logstash[689501]:       "@version" => "1",
Feb 06 16:20:31 ITS-ELST-01 logstash[689501]:          "event" => {
Feb 06 16:20:31 ITS-ELST-01 logstash[689501]:         "original" => "Feb  6 16:20:24 MY-SERVER postfix/smtp[2989787]: B90FEC014ADE: to=<XXXXXX@XXXX.XXX.XXX>, relay=mx02.au.com[27.86.106.196]:25, delay=0.22, delays=0.06/0.01/0.07/0.07, dsn=2.0.0, status=sent (250 Ok: queued as DB6471600A3)"
Feb 06 16:20:31 ITS-ELST-01 logstash[689501]:     },
Feb 06 16:20:31 ITS-ELST-01 logstash[689501]:        "message" => "Feb  6 16:20:24 MY-SERVER postfix/smtp[2989787]: B90FEC014ADE: to=<XXXXXX@XXXX.XXX.XXX>, relay=mx02.au.com[27.86.106.196]:25, delay=0.22, delays=0.06/0.01/0.07/0.07, dsn=2.0.0, status=sent (250 Ok: queued as DB6471600A3)",
Feb 06 16:20:31 ITS-ELST-01 logstash[689501]:           "host" => {
Feb 06 16:20:31 ITS-ELST-01 logstash[689501]:                   "mac" => [
Feb 06 16:20:31 ITS-ELST-01 logstash[689501]:             [0] "00:50:56:89:24:4a",
Feb 06 16:20:31 ITS-ELST-01 logstash[689501]:             [1] "00:50:56:89:d8:32"
Feb 06 16:20:31 ITS-ELST-01 logstash[689501]:         ],
Feb 06 16:20:31 ITS-ELST-01 logstash[689501]:                    "os" => {
Feb 06 16:20:31 ITS-ELST-01 logstash[689501]:              "version" => "8.6 (Green Obsidian)",
Feb 06 16:20:31 ITS-ELST-01 logstash[689501]:                 "name" => "Rocky Linux",
Feb 06 16:20:31 ITS-ELST-01 logstash[689501]:               "family" => "",
Feb 06 16:20:31 ITS-ELST-01 logstash[689501]:               "kernel" => "4.18.0-372.9.1.el8.x86_64",
Feb 06 16:20:31 ITS-ELST-01 logstash[689501]:             "platform" => "rocky",
Feb 06 16:20:31 ITS-ELST-01 logstash[689501]:                 "type" => "linux"
Feb 06 16:20:31 ITS-ELST-01 logstash[689501]:         },
Feb 06 16:20:31 ITS-ELST-01 logstash[689501]:                    "ip" => [
Feb 06 16:20:31 ITS-ELST-01 logstash[689501]:             [0] "202.32.104.72",
Feb 06 16:20:31 ITS-ELST-01 logstash[689501]:             [1] "192.168.49.12"
Feb 06 16:20:31 ITS-ELST-01 logstash[689501]:         ],
Feb 06 16:20:31 ITS-ELST-01 logstash[689501]:         "containerized" => false,
Feb 06 16:20:31 ITS-ELST-01 logstash[689501]:                  "name" => "MY-SERVER",
Feb 06 16:20:31 ITS-ELST-01 logstash[689501]:          "architecture" => "x86_64",
Feb 06 16:20:31 ITS-ELST-01 logstash[689501]:              "hostname" => "MY-SERVER",
Feb 06 16:20:31 ITS-ELST-01 logstash[689501]:                    "id" => "b4a712b2cebb41268aa683d962977dde"
Feb 06 16:20:31 ITS-ELST-01 logstash[689501]:     },
Feb 06 16:20:31 ITS-ELST-01 logstash[689501]:           "tags" => [
Feb 06 16:20:31 ITS-ELST-01 logstash[689501]:         [0] "kin",
Feb 06 16:20:31 ITS-ELST-01 logstash[689501]:         [1] "mail",
Feb 06 16:20:31 ITS-ELST-01 logstash[689501]:         [2] "beats_input_codec_plain_applied"
Feb 06 16:20:31 ITS-ELST-01 logstash[689501]:     ],
Feb 06 16:20:31 ITS-ELST-01 logstash[689501]:         "fields" => {
Feb 06 16:20:31 ITS-ELST-01 logstash[689501]:         "index_name" => "MY-MAIL"
Feb 06 16:20:31 ITS-ELST-01 logstash[689501]:     },
Feb 06 16:20:31 ITS-ELST-01 logstash[689501]:            "log" => {
Feb 06 16:20:31 ITS-ELST-01 logstash[689501]:           "file" => {
Feb 06 16:20:31 ITS-ELST-01 logstash[689501]:             "path" => "/var/log/maillog"
Feb 06 16:20:31 ITS-ELST-01 logstash[689501]:         },
Feb 06 16:20:31 ITS-ELST-01 logstash[689501]:         "offset" => 3624292
Feb 06 16:20:31 ITS-ELST-01 logstash[689501]:     },
Feb 06 16:20:31 ITS-ELST-01 logstash[689501]:      "logsource" => "MY-SERVER",
Feb 06 16:20:31 ITS-ELST-01 logstash[689501]:            "pid" => "2989787",
Feb 06 16:20:31 ITS-ELST-01 logstash[689501]:          "input" => {
Feb 06 16:20:31 ITS-ELST-01 logstash[689501]:         "type" => "log"
Feb 06 16:20:31 ITS-ELST-01 logstash[689501]:     },
Feb 06 16:20:31 ITS-ELST-01 logstash[689501]:        "process" => "smtp"
Feb 06 16:20:31 ITS-ELST-01 logstash[689501]: }
Elasticsearch(By Kibana)
{
  "_index": "MY-MAIL-2024.02.06",
  "_id": "fcJKfY0BX2moE9zJNd6f",
  "_version": 1,
  "_score": 0,
  "_source": {
    "timestamp": "Feb  6 16:20:24",
    "agent": {
      "version": "7.12.1",
      "name": "MY-SERVER",
      "hostname": "MY-SERVER",
      "ephemeral_id": "d4d40b29-a2d6-477d-b275-ce3c6bb2be1a",
      "id": "87215304-c7a1-4914-b057-ef6a368959eb",
      "type": "filebeat"
    },
    "@timestamp": "2024-02-06T07:20:30.758Z",
    "ecs": {
      "version": "1.8.0"
    },
    "@version": "1",
    "event": {
      "original": "Feb  6 16:20:24 MY-SERVER postfix/smtp[2989787]: B90FEC014ADE: to=<XXXXXX@XXX.XXX.XXX>, relay=mx02.au.com[27.86.106.196]:25, delay=0.22, delays=0.06/0.01/0.07/0.07, dsn=2.0.0, status=sent (250 Ok: queued as DB6471600A3)"
    },
    "message": "Feb  6 16:20:24 MY-SERVER postfix/smtp[2989787]: B90FEC014ADE: to=<XXXXXX@XXX.XXX.XXX>, relay=mx02.au.com[27.86.106.196]:25, delay=0.22, delays=0.06/0.01/0.07/0.07, dsn=2.0.0, status=sent (250 Ok: queued as DB6471600A3)",
    "host": {
      "mac": [
        "00:50:56:89:24:4a",
        "00:50:56:89:d8:32"
      ],
      "os": {
        "version": "8.6 (Green Obsidian)",
        "name": "Rocky Linux",
        "family": "",
        "kernel": "4.18.0-372.9.1.el8.x86_64",
        "platform": "rocky",
        "type": "linux"
      },
      "ip": [
        "202.32.104.72",
        "XXX.XXX.XXX.XXX"
      ],
      "containerized": false,
      "name": "MY-SERVER",
      "architecture": "x86_64",
      "hostname": "MY-SERVER",
      "id": "b4a712b2cebb41268aa683d962977dde"
    },
    "tags": [
      "kin",
      "mail",
      "beats_input_codec_plain_applied"
    ],
    "fields": {
      "index_name": "MY-MAIL"
    },
    "log": {
      "file": {
        "path": "/var/log/maillog"
      },
      "offset": 3624292
    },
    "logsource": "MY-SERVER",
    "pid": "2989787",
    "input": {
      "type": "log"
    },
    "process": "smtp"
  },
  "fields": {
    "agent.version.keyword": [
      "7.12.1"
    ],
    "host.architecture.keyword": [
      "x86_64"
    ],
    "host.name.keyword": [
      "MY-SERVER"
    ],
    "pid": [
      "2989787"
    ],
    "host.hostname": [
      "MY-SERVER"
    ],
    "host.mac": [
      "00:50:56:89:24:4a",
      "00:50:56:89:d8:32"
    ],
    "agent.hostname.keyword": [
      "MY-SERVER"
    ],
    "ecs.version.keyword": [
      "1.8.0"
    ],
    "host.ip.keyword": [
      "202.32.104.72",
      "XXX.XXX.XXX.XXX"
    ],
    "fields.index_name": [
      "MY-MAIL"
    ],
    "host.os.version": [
      "8.6 (Green Obsidian)"
    ],
    "host.os.name": [
      "Rocky Linux"
    ],
    "agent.name": [
      "MY-SERVER"
    ],
    "host.id.keyword": [
      "b4a712b2cebb41268aa683d962977dde"
    ],
    "host.name": [
      "MY-SERVER"
    ],
    "host.os.version.keyword": [
      "8.6 (Green Obsidian)"
    ],
    "logsource.keyword": [
      "MY-SERVER"
    ],
    "event.original": [
      "Feb  6 16:20:24 MY-SERVER postfix/smtp[2989787]: B90FEC014ADE: to=<XXXXXX@XXX.XXX.XXX>, relay=mx02.au.com[27.86.106.196]:25, delay=0.22, delays=0.06/0.01/0.07/0.07, dsn=2.0.0, status=sent (250 Ok: queued as DB6471600A3)"
    ],
    "host.os.type": [
      "linux"
    ],
    "agent.id.keyword": [
      "87215304-c7a1-4914-b057-ef6a368959eb"
    ],
    "@version.keyword": [
      "1"
    ],
    "input.type": [
      "log"
    ],
    "log.offset": [
      3624292
    ],
    "agent.hostname": [
      "MY-SERVER"
    ],
    "tags": [
      "kin",
      "mail",
      "beats_input_codec_plain_applied"
    ],
    "host.architecture": [
      "x86_64"
    ],
    "agent.id": [
      "87215304-c7a1-4914-b057-ef6a368959eb"
    ],
    "ecs.version": [
      "1.8.0"
    ],
    "host.containerized": [
      false
    ],
    "message.keyword": [
      "Feb  6 16:20:24 MY-SERVER postfix/smtp[2989787]: B90FEC014ADE: to=<XXXXXX@XXX.XXX.XXX>, relay=mx02.au.com[27.86.106.196]:25, delay=0.22, delays=0.06/0.01/0.07/0.07, dsn=2.0.0, status=sent (250 Ok: queued as DB6471600A3)"
    ],
    "fields.index_name.keyword": [
      "MY-MAIL"
    ],
    "host.hostname.keyword": [
      "MY-SERVER"
    ],
    "agent.version": [
      "7.12.1"
    ],
    "host.os.family": [
      ""
    ],
    "input.type.keyword": [
      "log"
    ],
    "tags.keyword": [
      "kin",
      "mail",
      "beats_input_codec_plain_applied"
    ],
    "process.keyword": [
      "smtp"
    ],
    "timestamp.keyword": [
      "Feb  6 16:20:24"
    ],
    "host.ip": [
      "202.32.104.72",
      "XXX.XXX.XXX.XXX"
    ],
    "pid.keyword": [
      "2989787"
    ],
    "agent.type": [
      "filebeat"
    ],
    "host.os.kernel.keyword": [
      "4.18.0-372.9.1.el8.x86_64"
    ],
    "host.os.kernel": [
      "4.18.0-372.9.1.el8.x86_64"
    ],
    "@version": [
      "1"
    ],
    "host.os.name.keyword": [
      "Rocky Linux"
    ],
    "host.id": [
      "b4a712b2cebb41268aa683d962977dde"
    ],
    "log.file.path.keyword": [
      "/var/log/maillog"
    ],
    "agent.type.keyword": [
      "filebeat"
    ],
    "timestamp": [
      "Feb  6 16:20:24"
    ],
    "agent.ephemeral_id.keyword": [
      "d4d40b29-a2d6-477d-b275-ce3c6bb2be1a"
    ],
    "process": [
      "smtp"
    ],
    "host.mac.keyword": [
      "00:50:56:89:24:4a",
      "00:50:56:89:d8:32"
    ],
    "agent.name.keyword": [
      "MY-SERVER"
    ],
    "logsource": [
      "MY-SERVER"
    ],
    "message": [
      "Feb  6 16:20:24 MY-SERVER postfix/smtp[2989787]: B90FEC014ADE: to=<XXXXXX@XXX.XXX.XXX>, relay=mx02.au.com[27.86.106.196]:25, delay=0.22, delays=0.06/0.01/0.07/0.07, dsn=2.0.0, status=sent (250 Ok: queued as DB6471600A3)"
    ],
    "host.os.family.keyword": [
      ""
    ],
    "@timestamp": [
      "2024-02-06T07:20:30.758Z"
    ],
    "host.os.type.keyword": [
      "linux"
    ],
    "host.os.platform": [
      "rocky"
    ],
    "host.os.platform.keyword": [
      "rocky"
    ],
    "event.original.keyword": [
      "Feb  6 16:20:24 MY-SERVER postfix/smtp[2989787]: B90FEC014ADE: to=<XXXXXX@XXX.XXX.XXX>, relay=mx02.au.com[27.86.106.196]:25, delay=0.22, delays=0.06/0.01/0.07/0.07, dsn=2.0.0, status=sent (250 Ok: queued as DB6471600A3)"
    ],
    "log.file.path": [
      "/var/log/maillog"
    ],
    "agent.ephemeral_id": [
      "d4d40b29-a2d6-477d-b275-ce3c6bb2be1a"
    ]
  }
}