I work for a small business and outsourced our email hosting to Google. However, I noticed that spammers are using our From: First Last to send their spam messages. All bounced messages come to our catch only account. How do I stop this? How do I validate our domain using SPF? How do I configure a SPF for Google Apps domain using BIND 9 or djbdns? [continue reading…]
My users will only be checking mail, and I want to disable FTP access as well as shell access under CentOS Linux. How do I disable shell (SSH) and FTP access to a new or old user under Linux without deleting user account? [continue reading…]
I have CentOS Linux acting as a router for our small community-based college. I see logwatch and other cron job generating emails for the root account. How do I delete those emails? I don’t want to disable email facility but just wanted to get rid of all root emails. How do I delete root user mails (mailbox) file in Linux or Unix like system? [continue reading…]
Q. I’ve Postfix based CentOS Linux server. I need to blacklist email ID: firstname.lastname@example.org . How do I blacklist email address with postfix? I also have spamassassin software installed.
A. By default, the Postfix SMTP server accepts any sender address. However you can block / blacklist sender email address easily with Postfix. It has SMTP server access table.
Open /etc/postfix/sender_access file # cd /etc/postfix
# vi sender_access
Append sender email id as follows: email@example.com REJECT
Save and close the file. Use postmap command to create a database: # postmap hash:sender_access
Now open main.cf and add code as follows: smtpd_recipient_restrictions = check_sender_access hash:/etc/postfix/sender_access
Save and close the file. Restart / reload postfix MTA: # /etc/init.d/postfix restart
You can also use spamassassin to blacklist email address. Just add to your own spamassassin configuration or to /etc/mail/spamassassin/local.cf file: # vi /etc/mail/spamassassin/local.cf
Append blacklist as follows: blacklist_from firstname.lastname@example.org
Save and close the file. Restart spamassassin: # /etc/init.d/spamassassin restart
spamassassin will marke mail as SPAM instead of rejecting the same.
Q. I would like to install latest and greatest Mozilla thunderbird mail client under Linux.
How do I download and install the same to read emails?
A. Mozilla’s Thunderbird 2 email application is more powerful than ever. Thunderbird 2 features many new enhancements to help you better manage your unruly inbox, and stay informed. Thunderbird 2 scales to the most sophisticated organizational needs while making it easy to find what you need. It is the best mail/news client with RSS and integrated spam filter support.