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WebPanel => Postfix => Topic started by: DNA on March 06, 2022, 10:49:19 AM

Title: Spam Filtering by Subject Line
Post by: DNA on March 06, 2022, 10:49:19 AM

Spammers are so intelligent and They are sending Spam with the following subject line :

your Dropbox has stopped syncing
Income Tax return 2021 issued
Please Check Your Identity Immediately
suspended incoming messages
Your Password is about to expire
Account Suspension Notice
Shipment has been completed
Advertise up to 200 MILLION EMAILS

If we block above subject by REJECT command , Spammer will get notification, Sometimes spammers has no return valid path . So we will DISCARD those email by the following settings :

Code: [Select]

# vi /etc/postfix/header_checks

/Bitcoin/                                                                    DISCARD
/Dropbox has stopped syncing/                          DISCARD
/Wetgeving/                                                               DISCARD
/Income Tax return 2021 issued/                                  DISCARD
/PSD2/                                                                         DISCARD
/Please Check Your Identity Immediately/                        DISCARD
/suspended incoming messages/                                     DISCARD
/Your Password is about to expire/                                  DISCARD
/Bescherm uw account/                                                  DISCARD
/Account Suspension Notice/                                          DISCARD
/Shipment has been completed/                                     DISCARD
/Advertise up to 200 MILLION EMAILS/                            DISCARD
/To:.*<>/                                                                     DISCARD
/From:.*<>/                                                                DISCARD
/^Subject:/                                                                 WARN
 

Code: [Select]

# postmap /etc/postfix/header_checks
# systemctl restart postfix

Title: Re: Spam Filtering by Subject Line
Post by: iraqiboy90 on March 06, 2022, 02:58:21 PM

I don't think spammers cares about the Reject status, because most of the times it's bots. Same for the greylisting. Most of them won't try again after a 4.x.x response.

So, greylisting (a bit aggressive for my taste) + spamassassin + spamhaus/blacklist checks = The best spam protection without false positives.

You can't have 100% spam protection without false positives.

Title: Re: Spam Filtering by Subject Line
Post by: studio4host on March 07, 2022, 07:47:16 AM

you are missing the important part of having that file included in the postfix conf to work

/etc/postfix/main.cf:

Code: [Select]

header_checks = pcre:/etc/postfix/header_checks

Title: Re: Spam Filtering by Subject Line
Post by: dp41646 on March 07, 2022, 10:03:36 AM

Quote from: iraqiboy90 on March 06, 2022, 02:58:21 PM

I don't think spammers cares about the Reject status, because most of the times it's bots. Same for the greylisting. Most of them won't try again after a 4.x.x response.

So, greylisting (a bit aggressive for my taste) + spamassassin + spamhaus/blacklist checks = The best spam protection without false positives.

You can't have 100% spam protection without false positives.

Hi,
does CWP have greylisting?
Is it possible to activate it?
I think that this should solve many of spam problems, I am currently facing.

Thx

Title: Re: Spam Filtering by Subject Line
Post by: iraqiboy90 on March 07, 2022, 10:12:56 AM

Quote from: dp41646 on March 07, 2022, 10:03:36 AM

Quote from: iraqiboy90 on March 06, 2022, 02:58:21 PM

I don't think spammers cares about the Reject status, because most of the times it's bots. Same for the greylisting. Most of them won't try again after a 4.x.x response.

So, greylisting (a bit aggressive for my taste) + spamassassin + spamhaus/blacklist checks = The best spam protection without false positives.

You can't have 100% spam protection without false positives.

Hi,
does CWP have greylisting?
Is it possible to activate it?
I think that this should solve many of spam problems, I am currently facing.

Thx

You are going to need to manually install it.
https://wiki.centos.org/HowTos/postgrey?action=fullsearch&context=180&value=spf

Title: Re: Spam Filtering by Subject Line
Post by: cantay on June 26, 2022, 07:46:00 PM

Quote from: iraqiboy90 on March 07, 2022, 10:12:56 AM

Quote from: dp41646 on March 07, 2022, 10:03:36 AM

Quote from: iraqiboy90 on March 06, 2022, 02:58:21 PM

I don't think spammers cares about the Reject status, because most of the times it's bots. Same for the greylisting. Most of them won't try again after a 4.x.x response.

So, greylisting (a bit aggressive for my taste) + spamassassin + spamhaus/blacklist checks = The best spam protection without false positives.

You can't have 100% spam protection without false positives.

Hi,
does CWP have greylisting?
Is it possible to activate it?
I think that this should solve many of spam problems, I am currently facing.

Thx

You are going to need to manually install it.
https://wiki.centos.org/HowTos/postgrey?action=fullsearch&context=180&value=spf

Hi iraqiboy90,

When I add the desired settings to the postfix mail configuration. Will I have a problem with the CWP mail server structure?

When I add the following parameters to the current configuration settings, it gives an error in the logs. Is it possible for you to share your configuration structure?

/etc/postfix/main.cf

smtpd_recipient_restrictions =
    permit_mynetworks,
    reject_unauth_destination,
    check_policy_service unix:postgrey/socket,
    permit