AntiSPAM support is provided as a free service at this time for all our Virtual Mail Services.
AntiSPAM support cannot be disabled via Web.Manager. However you can generate whitelists based
on From / To headers in Web.Manager. Webvisions cannot guarantee that the use of AntiSPAM service
will result in a 100% spam free environment nor can we guarantee that false positives (blocking
of valid emails) will never occur. However, in the event that an email is blocked, the sender
will recieve a notification that the recipient has rejected his email.
FAQs for Integrated AntiSPAM Support in Virtual Mail Server
Q. What is this all about ?
A. Spam or UCE (Unsolicited Commercial Email) are threats to many computer systems today. They consume
an abundance of server, network and bandwidth resources and waste an individuals' time that could have been allocated
to more productive uses as opposed to weeding out hundreds of unwated spams in his/her mail box.
With Webvisions' Integrated AntiSPAM support built into your Virtual Mail Server,
it provides an extra layer of protection for your email and reduces dramatically the amount of spam
sent to you.
Q. How does the AntiSPAM support work ?
A. Webvisions employs a four tiered approach towards tackling the spam problem. These four tiers are as follows.
- Realtime Blackhole/Block List (RBLs) using Spamhaus (www.spamhaus.org)
- Global Spam Filters (keyword based)
- Server Level Spam Tagging based on Heuristical and Bayesian (Statistical) analysis with SpamAssassin - New from Mar/Apr 04
- End User White-listing / Black-listing
Realtime Block List
Realtime Block Lists or DNS Blocking Lists are designed to work most effectively during SMTP "realtime" transmission, enabling spam to be rejected early in the transaction,
before it burdens servers, disks and mail queues. Because the SMTP transmission is terminated before the spam can be transmitted, this also results in a "Delivery Status Notification" (error
message) which notifies the sender's server of the rejection and provides a fail-safe in case of errors or false positives. RBLs are very effective
as a first line of defence. Many ISPs today use Spamhaus, which is a well known and widely used RBL around the world.
Global Spam Filters
Global Spam Filters sit on all our email gateways. It is a keyword/phrase based system that tracks and blocks
unwanted spam content. Keywords or phrases are generated from common anti-spam databases. This is a simple
and fast filter that works very effectively against heavy spammers. It generates a higher level of false positives
although the success rates are also the highest against well known spams.
Server Level Spam Tagging
We employ SpamAssassin (www.spamassassin.org) here as a server level spam tagging solution.
SpamAssassin is a mail filter which attempts to identify spam using text analysis and several internet-based realtime blacklists.
Using its rule base, it uses a wide range of heuristic tests on mail
headers and body text to identify "spam", also known as unsolicited
commercial email.
Once identified, depending on numerical thresholds set, the mail will either
be tagged and rejected or sent to the recipient with the following
phrase "***[SUSPECTED SPAM]***" prepended to the email's subject
header. On retrieving the email, the end user can then automatically
route these emails to a separate folder for manual filtering.
Numerical Thresholds in SpamAssasin:
- 5 - Low Threshold
- 7.5 - Moderate Threshold
- 10 - High Threshold
- 15 - Very High Threshold
SpamAssassin typically differentiates successfully between spam and
non-spam in between 95% and 99% of cases, depending on what kind
of mail you get. We set a very high threshold of 15 for rejecting
spam mails and anything between a score of 5 to 15 (moderate to high
threshold) gets tagged and sent to the intended recipient as suspected
spam.
This system also includes a powerful auto-learning feature that learns
from its previous history of known and unknown spams and automatically allow it to
better identify future spams. This feature grows with every email that is received.
These filters are currently subjected onto emails sent to recipients in each
server. If you are sending a mail out, (i.e. local sender), you will not
be subjected to these filters.
End User White-listing / Black-listing
Via Web.Manager (Email Management -> Setting Mail Blocking Rules), our customers are also able to white-list (allow all) or black-list
(disallow all) emails based on specific email headers like "From" or "To". White-lists are useful for specifying addresses which send
mail that is often tagged
(incorrectly) as spam. Black-lists are exactly the opposite, it blocks emails you do not want to see. This feature
will override the Server Level Spam Tagging filters above.
These filters are currently subjected onto emails sent to recipients in each
server. If you are sending a mail out, (i.e. local sender), you will not
be subjected to these filters.
Q. What are false positives ? Can they be eliminated ?
A. False positives are emails wrongly identified as spam. Most spam filters today are 95% to 99% accurate. Unfortunately,
by nature of spam and spam filters themselves, it is impossible to prevent false positives. However, we can try and
reduce the occurance of false positives to a very very low level.
Q. What should I do if a valid sender (i.e. a false positive) is caught in your Global Spam Filters?
While preventing the spread of UCE or Spam, good intended emails may get caught in our spam filters.
If an email account has been blocked by our spam filters, please kindly write in to support@webvisions.com
with details of the sender and recipient and we'll have it removed.
Q. Can I do away with my desktop based Antispam tools now that we have this from Webvisions ?
A. Certainly not. This just adds one layer of protection. It is always good to approach spam or security in general
with a layered approach.
Q. Will a notice be sent to the recipient as well if an email is rejected ?
A. No, notices are sent only to senders when an email is rejected.
Q. Are all Webvisions Virtual Mail Servers installed with this service ?
A. Yes, when completed, all Webvisions Virtual Mail Servers will be *except* for mail servers on the following
IP Address (202.157.163.221) which has been designated for customers who do not wish to have this service.
Customers with mail servers on this IP may request to upgrade to a machine with this service at
support@webvisions.com. There is no additional cost for this upgrade.
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