SMTP Restrictions disabled problems with spam list

Otávio Serra

Active Member
Apr 27, 2015
cPanel Access Level
Root Administrator
Hi every one,

Last week I needed to disable SMTP Restrictions on WHM because one account have one website here in my server, but mail's server in another server. Today I detected that my server entered in SPAMCOP list.

I located in WHM's Mail Delivery Reports a lot of mail rejection and in Delivery Event Details I saw this Authentication: forwarder

[Removed Due To Use Of Real Domain Names]
Result: SMTP error from remote mail server after end of data: 421-4.7.0 [removed 15] Our system has detected that this message is\n421-4.7.0 suspicious due to the very low reputation of the sending domain. To\n421-4.7.0 best protect our users from spam, the message has been blocked.\n421-4.7.0 Please visit\n421 4.7.0 Why has Gmail blocked my messages? - Gmail Help for more information. f89si7077027plf.1039 - gsmtp

All of this bunch of mails don't was sent from my server [removed] . I searched for these mails on Mail Delivery Reports and it was not found. This is one example of messages returns from server's recipients that defered this bunch of mails. There are a lot of similar messages.

So, I understood that SMTP Restrictions need to be enabled to fix this. But in need to forward mail for 2 accounts. It's possible to do it with WHM/cPanel or I need other 3rd party solution? Anyone knows what can I do to fix it? Or I have another possibility to fix it?


Staff member
Apr 11, 2011

The SMTP Restrictions feature is not designed for modifications or whitelisting of additional users. I suggest using a third-party firewall management utility such as CSF instead:

ConfigServer Security & Firewall

There are options that allow you to restrict SMTP similar to the SMTP Restrictions option in WHM.

Thank you.