Postfix smtpd_client_restrictions

Keeping known email abusers out is always desired. Postfix has a parameter which is specified in the main.cf file that allows you to refer to these lists.
The script I use is as follows…

smtpd_client_restrictions =
permit_mynetworks
permit_sasl_authenticated
reject_unauth_pipelining
reject_rbl_client cbl.abuseat.org
reject_rbl_client dnsbl.ahbl.org
reject_rbl_client dnsbl.sorbs.net
reject_rbl_client list.dsbl.org
reject_rbl_client sbl-xbl.spamhaus.org
#reject_rhsbl_client blackhole.securitysage.com
reject_rhsbl_client rhsbl.sorbs.net
permit

Note the commented out line

#reject_rhsbl_client blackhole.securitysage.com

See below
Sponsored Links

This is a list that was not properly [...]

Bandwidth Conversion

See below
Sponsored Links

Bandwidth Conversion

Mbit
K/s

100
12,800

20
2,560

16
2,048

8
1,024

4
512

2
256

1
128

0.5
64

Backup your Linux Server Apps

So you have your linux server up and running. A lot of time and effort went into this so lets get it backed up. You don’t need to invest in any fancy backup system. A bit of shell script and some use of crontab will do the trick.
Here are the two scripts I use…

Email backup
Create [...]

Telnet your email server

Very often it is necessary to test that your SMTP server is working.
The easiest way to do this is with the telnet command.
This lets you talk directly to the email server in its own SMTP protocol script language.
Here’s how…
telnet server name or IP address 25
HELO aaaa
mail from: <tom@fromdomain.com>
rcpt to: <fred@todomain.com>
data
Enter your message text
.
quit
Along the way [...]

PostCast Server

This is an SMTP server like the one your ISP provides. It is targeted at Windows users and sells as a faster and more flexible alternative.
I don’t like to be negative about the efforts of others but, I do find it diffucult to see what advantage this server application gives you over the already available [...]

Email server software

There are a huge range of email server products available.
I won’t beat around the bush, in my honest opinion, most Postfix based systems are by far the most practical and effective. The main reason for this is that Postfix is free and flexible.
A fantastic, sophisticated and clever email server software system is the Zimbra Collaboration [...]

VoIP issues

Discovered something unexpected and annoying.
I recently installed an office VoIP system using 3CX and a mix of X-Lite and 3CX client apps. To cut a long story short, I sorted the bandwidth issue but two desktops continued to have issues. This was perplexing and rather annoying as one was the IT Director’s.
Convinced there was still [...]