If you are using an email client besides Outlook (gasp!), you have most likely run into the attachment winmail.dat. Supposedly this can be prevented on the client side by sending mail in plain text; however, this doesn’t appear to work with attachments. We ran across a cool utility at Fentun that will extract attachments out […]

Make sure that you are not running an old version of formmail.pl. Check your cgi-bin directory to make sure. Even though the fix for formmail has been out since last August, we are still getting scanned for this on our webservers. Old versions of formmail.pl can be used to send spam. For more info, check […]

All of the DNS blacklists we used a couple years ago are defunct. There are, however, a slew of new DNS-based blacklists that can help protect your users from spam. Understand that with any blacklist there is a chance that legitimate email will be blocked. Balancing this against the cost and annoyance of spam is […]

If you have a sendmail server that has a hostname that isn’t resolvable, you may need to masquerade as a different host. This is often the case if you are running sendmail on your internal workstation. We also ran into this while bringing up a Squirrel Mail web based mail system. Simply add these lines […]

Outlook is nice and all, particularly when dealing with, oh, 90 percent of the email clients out there. The same thing that makes it nice, also makes it insecure. Some of the email accounts we monitor have been quite public, and receive not only a lot of spam, but also a lot of viruses. If […]

It is quite easy to email security or traffic reports automatically. We will use mpack, sendmail, and cron, but certainly the techniques could be combined with other utilities. The challenge with emailing files is that you have to encode the attachments into the email message using MIME. For the nitty gritty on MIME, see http://www.nacs.uci.edu/indiv/ehood/MIME/MIME.html. […]

First, we want to remove all the RPM stuff. A general note here. We are removing the RPMs, because we want to write all of the articles from the perspective of a generic Linux distribution as much as possible. True, we rely on the default file structure and general layout of Red Hat; however, by […]

First, we grab the source from the UW distribution link on here: [root@srv-33 src]# ls imap.tar.Z imap-utils.tar.Z [root@srv-33 src]# tar -xzf imap.tar.Z [root@srv-33 src]# ls imap-2001.BETA.SNAP-0105251616 imap.tar.Z imap-utils.tar.Z [root@srv-33 src]# mkdir imaputils (We will deal with imaputils in a different section.) [root@srv-33 src]# mv *util* imaputils mv: cannot move `imaputils’ to a subdirectory of itself, […]