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Most of the spam rejection in SimbeyMail is done on a per-user basis. You can set up
users that will receive all E-Mail, and you can set up users that will only receive E-Mail
that has met a set of selected criteria.
The following is the list of flags that can be set for users:
- MUI_ALLOW_ALL
This means that, with only a few exceptions, all E-Mail is
accepted. If other flags are set, they are ignored.
- MUI_CHECK_PASSCODE
Pass codes are an extension to SMTP and aren't supported
by anything else. The syntax is RCPT TO:<address> #### where ####
is the pass code number. If this flag is set, a client SMTP server must specify the
correct pass code.
- MUI_CHECK_APPROVED
A user can accept E-Mail whose sending server is on the
global server approved list when this flag is set.
- MUI_CHECK_DENIED
A user can reject E-Mail whose sending server is on the
global server denied list when this flag is set.
- MUI_CHECK_SOURCE
When this flag is set, SimbeyMail will take the address
from the MAIL FROM:<> command and verify whether it exists before
returning a response to the RCPT TO:<> command. Basically,
SimbeyMail looks up the MX and connects the server based on the sender's address. It
identifies itself as sending from the postmaster address and will issue a RCPT
TO:<> command. If the response is negative, SimbeyMail responds to the
sending client with a negative response.
- MUI_SECURE_SMTP
This flag requires that the user authenticate itself when
sending E-Mail through SimbeyMail. It prevents unauthorized users from sending
E-Mail through SimbeyMail while claiming to be a SimbeyMail user.
- MUI_VERIFY_DENIED
SimbeyMail resolves the host name from the sender's IP
address and checks whether any portion of the host name is on the global denied server
list.
- MUI_CHECK_PLUGIN
This is a callback SimbeyMail can make into the E-Mail host
program. It is not currently used by SMailSvc.exe or ServerGui.exe.
- MUI_WHITE_LIST_DIRECT
Users can set up E-Mail white lists and reject
anything not on the white list.
- MUI_WHITE_LIST_PROXY
This works just like the direct flag, but it works on
E-Mail copied from remote POP3 accounts. If E-Mail from remote accounts is rejected,
rejection notices are sent to the sender and optionally to a carbon copy address that can
be configured inside SimbeyMail.
- MUI_PROXY_BLOCK_FOLDER
If proxied E-Mail is rejected, this flag instructs
SimbeyMail to place the E-Mail is a special blocked folder, rather than completely delete
the E-Mail.
- MUI_CHECK_HELO_NOT_IP
If the sending SMTP server identifies itself with an
IP address (which is usually fake), this flag will reject the E-Mail when the sender tries
to include users with this flag.
- MUI_REVERSE_SENDER_CHECK
This flag is experimental and in most cases will
end up rejecting legitimate E-Mail. SimbeyMail attempts to check the sender's E-Mail
address by connecting to port 25 on the sender's IP address. In most cases, the
sender's IP address is not the same server that hosts the incoming SMTP server.
- MUI_CHECK_SENDER_TYPE
This is my favorite rejection rule! Only
senders whose name, including their original HELO identification, ends in
.com, .org, .edu, .net, .mil, .gov, or .int will be accepted. If a user does not
receive E-Mail from outside the United States, and if a user does not acknowledge the
newer "top level domain extensions" such as .biz, then this flag will reject spam like
nothing else!
- MUI_CHECK_WHOIS
With this flag set, SimbeyMail will make a standard WHOIS
query against the sender's IP address (SimbeyMail may follow referral links). The
actual processing of the WHOIS data is done by the host. Both SMailSvc.exe and
ServerGui.exe provide a customized VBScript host for allowing user written VBScripts to
process the requests. This is a great way to nearly guarantee that no one from
outside the United States (or any particular political region) will be able to send you
E-Mail (think about spam from Russia, for example).
- MUI_FORWARD_MAIL
This has nothing to do with blocking spam. When set,
E-Mail delivered to the SimbeyMail user will be forwarded to another E-Mail address.
- MUI_PROXY_STRICT
This flag is basically a combination of
MUI_CHECK_HELO_NOT_IP and MUI_CHECK_SENDER_TYPE for proxied E-Mail. SimbeyMail is a
little more lenient for E-Mail coming from addresses local to the proxied account server
(this is necessary for Comcast).
- MUI_BLACK_LIST_PROXY
This flag tells SimbeyMail to check proxied addresses
against the black list.
- MUI_BLOCK_BY_AGENT
Not implemented. It's a place holder for the day
when SimbeyMail rejects E-Mail based on the client agent that "generated" the
E-Mail. Spammers like to forge this line with obscure agents, so it may prove
useful.
- MUI_IP_BLACK_LIST
SimbeyMail rejects E-Mail when the sender's IP is in a
black IP range. The list is globally managed, so only administrators can update the
list.
- MUI_IP_PROXY_LIST
SimbeyMail uses the black IP list to reject proxied
E-Mail. This flag has saved me from hundreds of pieces of junk that Comcast doesn't
know how to block.
SimbeyMail keeps track of rejected senders in a separate REJECT.LOG text file. Even
rejected senders from proxied accounts show up in the reject log. The log is a great
way of seeing how many spam attempts have been foiled by SimbeyMail for a given period of
time.
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Simbey.com
