Dealing with Email SPAM
Dealing with Email SPAM – options for your email server and email account(s).
Note – most of these items are beyond what an average user can do; talk with your email provider about these options; in many cases they are simple to implement as well as being reasonably effective at reducing SPAM email messages. The free email approach (discussed below) may be a good solution for personal use. If you are responsible for your company email server then the remaining items may be helpful.
Use some or all of these solutions:
- use a free email account with good SPAM filtering to forward to your real email address (user approach)
- special email addresses for anonymous or specific uses (user approach)
- incoming email filter (i.e. Spamassassin, server and user approach)
- greylisting (server/network approach)
- network email ACL (server/network approach using IP access control lists)
- RBLs services (server/network approach)
- custom milters (server approach, Sendmail configuration changes)
- block email connections from non-relevant domains and/or geographic locations (network/server approach)
In general, as soon as you create a post anywhere on the Internet you are exposing your email address to SPAM-harvestors (automated programs or persons who seek and collect email addresses to send SPAM messages to.) I use a number of email aliases (an alternate email address that will still reach my real email inbox.) By using aliases (which I create on my server) I can track who is giving out/using the email address. This also provides an easy means to filter incoming messages for special handling.
Many people opt to use one (or more) of the free email accounts instead of using aliases, for instance, you can configure your GMAIL account to forward messages to your real email account. My experience is that GMAIL is does a very good job of filtering out SPAM messages. While possible, I think that this approach should be avoided for professional or business communications since it will dilute your domain branding…
Greylisting - is a network approach; you install special software that works with your email server. When an in-coming message arrives, the grey-list is checked; if the in-coming IP address is known as good then the messages is sent to the next delivery step; if the in-coming IP address is not known then the sender is told to come back later (many SPAM messages will never try a second time.) The downside to this approach is that all messages are subject to delays until the IP address of the sender is validated by appropriately re-trying. Good messages can also fail or be rejected if the IP address of the sender changes. The good news is that you can customize the configuration to deal with these types of problems. I saw a significant reduction in SPAM after implementing this approach.
RBLS services – real-time blackhole lists – is a network approach; usually managed by a third party that maintains a list of known SPAM IP address sources; when an in-coming email arrives your server checks the black list – if the in-coming IP is on the black list then the message is rejected. Some of these solutions require paid subscriptions.
Network email ACL – is a server/network approach using a custom IP access control list on your server. As you identify IP addresses of SPAMMERS you block them by adding them to this list. It is quite common to see SPAM messages from the same IP address space - when this occurs you can block an entire sub-net, i.e. I get SPAM from aa.bb.ccc.ddd, aa.bb.ccc.dde, aa.bb.ccc.ddf, aa.bb.ccc.ddg, and aa.bb.ccc.ddh. Clearly the IP range is being used by a SPAMMER or Bot so I will block the entire sub-net: ‘aa.bb.ccc.’ – any matching IP address would be rejected.
Other network approaches – instead of blocking just email you can block all services for an IP address or IP range, i.e. unless there is a business need then consider blocking all connections from Country ZZZ (known to be a source of SPAM, bot-net or other malicious activities.)
The main benefits from blocking un-wanted email (in addition to lowering your frustrations with the barrage):
- reduced server/network traffic
- reduced threat from email borne viruses/mailware (since they tend to originate from SPAMMY IP addresses)
Note – even with the above approaches you should still consider using email filters and updated virus checkers on your PC, and of course, avoid clicking on email links when emails are from suspicious, unexpected or unknown senders.
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