Ability for spam messages to not be forward via mailing list

[d19dotca]

I'd like to request the ability for Cloudron to not forward on mail to a mailing list recipient if it's identified it as spam.

Context behind feature request:

I have a particular recipient who checks their email on iCloud.com but has a domain I host for them too which is simply a bunch of mailing lists that forward to their iCloud.com accounts.

They’ve been getting a lot of spam lately. Thankfully Apple blocks most of it so they don’t really see the extra spam, but in my mail server logs I see that there are frequently messages sent which the system identifies as spam (and obvious spam at that - see log below), but still forwards it on anyway. This then causes Apple to send a bounce which my mail server forwards on and basically goes in a bit of loop.

For multiple reasons, I’d like the system to not forward messages to mailing lists when it it identifies the message as spam. Ideally also the ability to set a threshold number to avoid false-positives. Some reasons include:

• unnecessary resource usage of the mail server
• risk of being blocked by receiving mail server as sending spam (this is the biggest reason IMO)

{
  "ts": 1615659016646,
  "type": "queued",
  "direction": "inbound",
  "uuid": "080BB72D-E208-4C11-8CA0-080450DC03E6.1",
  "remote": {
    "ip": "162.215.212.45",
    "port": 45066,
    "host": "162-215-212-45.unifiedlayer.com",
    "info": "162-215-212-45.unifiedlayer.com",
    "closed": false,
    "is_private": false,
    "is_local": false
  },
  "authUser": null,
  "mailFrom": "<SRS0=326c=IM=worldmap2100.info=WORLDMAP210020210313@<domain>.<tld>>",
  "rcptTo": [
    "<<username>@<domain>.<tld>>"
  ],
  "details": {
    "spamStatus": "Yes, score=20.8 required=5.0 tests=BAYES_99,BAYES_999,  \tCK_HELO_DYNAMIC_SPLIT_IP,DYN_RDNS_AND_INLINE_IMAGE,  \tFREEMAIL_FORGED_REPLYTO,FREEMAIL_REPLYTO_END_DIGIT,FROM_LOCAL_DIGITS,  \tFROM_LOCAL_HEX,GB_FREEMAIL_DISPTO,GB_FREEMAIL_DISPTO_NOTFREEM,  \tHELO_MISC_IP,HTML_IMAGE_ONLY_04,HTML_MESSAGE,HTML_SHORT_LINK_IMG_1,  \tIMG_ONLY_FM_DOM_INFO,KHOP_HELO_FCRDNS,MIME_HTML_ONLY,  \tRCVD_IN_BL_SPAMCOP_NET,RCVD_IN_MSPIKE_BL,RCVD_IN_MSPIKE_L5,  \tRCVD_IN_RP_RNBL,RDNS_DYNAMIC,SPF_HELO_NONE,TVD_RCVD_IP,T_SPF_TEMPERROR,  \tURI_HEX autolearn=no autolearn_force=no version=3.4.4",
    "message": "Message Queued (080BB72D-E208-4C11-8CA0-080450DC03E6.1) (080BB72D-E208-4C11-8CA0-080450DC03E6.1)"
  }
}