This is the short description of Msen's mail policies with links on how
to configure your machine. The process is listed in order of action so
you can see which parts take precedence.
Inbound
Greylisting has become our first line of defense for spam.
Greylisting
is a process that delays email for 10 minutes before accepting it unless the address
is listed in the override file.
It is an attempt to block spammers who will only make one attempt at
sending email before they go on to another victim. Any legitimate
email server will retry any delayed mail, and so legitimate email
gets through, while most spam is denied. Once a particular address
has sent you a piece of email, it is white listed for a week.
Measurements show that 93% of spam is being blocked using this method alone.
Overrides:
the source IP address is an Msen IP address.
the sender has used POP before SMTP to authenticate herself
the sender has used SMTP-AUTH to authenticate himself
hand built override tables for known good addresses, Ie. eBay
Spamilter runs several checks on a mail message during
the receive process looking for indications of spam. Here are the list of
reasons a message may be rejected:
Access file controls do block a few blocks of IP addresses known
to be owned by hardcore spammers. Addresses listed here are blocked
with no chance of getting through. Reserved for only the most hardcore
spammers. Since these people tend to move constantly, the list and
effectiveness is small.
Virus removal is done for known viruses that have an
easily identifiable signature. These are removed from all inbound email
and there are no override possibilities. The current list is: Bagle, Bugbear,
Dumaru, Hybris, Klez, Mimail, Moodown, Novarg, Sobig, Swen, and Yaha.
Two general virus techniques are also killed. Exploit-IFrame and zip files
containing more than 10 spaces in the filename inside the archive.
Msen highly recommends that all PCs have up to date
virus filtering software
installed on them. Our virus filtering only catches the noisiest problem viruses.
Executable attachments are blocked and deleted.
Any email with an file attachment that has an extension of: bat pif cmd vba vbs scr lnk com exe chm
will automatically be deleted. If you need to send/receive one of these file
types, use Zip to archive the file first.
Tagged email: All further email is received and tagged
as possible spam according to:
Listed in Spamcop.net's database
Listed in the Spamhaus.org's
database as either an known spammer or a virus/worm/proxy compromised machine.
Listed in the Open Relay Database.
Contains offensive phrases in the
subject or body that procmail can find.
A longer description of tagging can be found on its
own page.
Msen user's choose with the following
control panel
what tagged spam is saved to their mailbox, and what is deleted automatically.
Personal Filtering: If too much spam still gets through all
that, the user should install a personal spam filter on their computer that can be
tailored to their needs. A recommendation of a few are on the
spam control panel page.
Outbound
To use Msen's servers for outgoing email, you must be one of the following:
using an IP address that is an Msen IP address. Ie. dialup to our modems
have used POP3 before SMTP to authenticate yourself to the server for 30 minutes. Ie. read your mail
before sending mail out.
using SMTP-AUTH to authenticate yourself to the server.
This sends your POP3 userid/password as part of the outgoing mail process.
All email domains processed by Msen have SPF (Sender Policy
Framework) records set for them to prevent forgery by spammers and viruses.
We have a severe policy for when we catch a customer spamming.
Msen charges offenders $100.00 plus $150.00 per hour cleanup costs per occurrence.
These charges apply, even if we choose to terminate the account. See our
spam policy for details.
No outbound virus checking is done on Msen's mail servers.
Anti-virus checking is the responsibility of the user. If a user's machine is
found to be infected with a virus, that customer falls under the network abuse
part of our spam policy. The customer may be fined for the network abuse their
machine is causing with the virus.
Mail Encryption
See our page on TLS/SSL mail transport encryption.
