| Sending Outbound Email |
Most ISPs are implementing "port 25
blocking", which is generally considered a "best practice" in the ISP industry
at this time. Port 25 blocking requires the ISP customers to send OUTBOUND email through
the ISP mail server.
Port 25 Blocking disrupts viruses and malware programs that get on ISP customer
machines and send out spam emails. The emails must now be sent through the ISP's
mail server so they can monitor the volume of email and control spam sent
through their systems.When your ISP implements Port 25 Blocking, will will
suddenly, and without warning, be unable to send OUT email. You will still
receive email. You may get a message that your outbound mail server can not be
found or does not exist, or you may get connection failures and dis-connects. Since you are receiving email from that same mail
server, you can be sure that it does exist and can be found. Since you can't
SEND email out through it, your mail program is simply returning this error
message to notify you that it couldn't send email using that mail server.
When you SEND email: You can only SEND email OUT through your Internet Access
Provider's outbound (SMTP) mail
servers. You can not SEND email OUT through any other mail servers except theirs.
When you RECEIVE email: You can continue receiving email at your domain name
with your current settings. You do not need to change anything to continue
receiving email at your domain name.
To SEND email, you must change your OUTBOUND SMTP mail server, under "Account
Server Settings" in your mail program.
|
| Dedicated IP Customers |
|
If you pay extra for a dedicated IP Numbers from your ISP, you can probably
have Port 25 Blocking disabled. You may not want to do this, and you do not have
to.
|
| Sending Mail Out Through Your
CommerceStreet.com Mail Server |
|
Regardless of Port 25 Blocking, you
can still send email out from your domain name through
your mail server hosted at CommerceStreet.com.
CommerceStreet.com email servers listen on "alternate
SMTP ports", which can only be accessed by our customers
with an email address on the server and the
corresponding password. To access your mail
server via the alternate port, change the OUTBOUND SMTP
PORT NUMBER from 25 to 2525 in your mail program.
In Outlook, this is under "Advanced Settings".
For the latest version of Outlook (2007):
- From Outlook's main menu, select Tools
and then Account Settings
- In the pop-up window that appears, select the
email account and click the Change..
button.
- The Internet E-mail Settings window appears,
click the More Settings... button.
- A new window opens, click the Advanced
tab.
- In the Server Port Numbers
section, change the Outgoing server (SMTP)
port number from 25 to 2525.
- Click the Outgoing Server tab.
- Verify that My outgoing server (SMTP)
requires authentication is checked and
Use same settings as my incoming mail server.
- Click the OK button, which
closes the window.
- Click the Next button, then the
Finish button, which closes that
window.
- Click the Close button which
returns you to Outlook.
After changing the port settings, you may need to
open each email message in your out folder and re-click
the send button.
If you are using a different email program than
Outlook 2007, the same settings are available and can be
changed. Other versions of Microsoft Outlook, including
Outlook express and Microsoft Mail are very similar to
the instructions included above.
|
| Why Block Port 25? |
|
Internet Service Providers are
blocking Port 25 to reduce spam and viruses.
- Spammers sign up for high speed Internet access
accounts (such as DSL and Cable) and run their own
mail server (smtp engine) to deliver their spam
messages. This smtp engine connects to each spam
recipient's mail server and delivers the spam
directly to the recipients mail server. The ISP can
not see the spam messages being delivered.
When the ISP blocks Port 25, these smtp engines can
not connect to recipient's mail servers and can not
deliver spam messages. Instead, the spammer must
send mail out through the ISP email server. The ISPs
run mail server monitors to detect spammers so they
turn them off quickly. This can reduce the flow of
spam.
- During the last few years, "Commercial Viruses" have
infected millions of computers. Commercial viruses do not
disrupt your computer operations or do anything
"bad" to your computer. Most people do not even know
their computers are infected with these viruses.
Commercial Viruses let spammers connect up to the
infected computer and send spam messages out using
the infected computer. These infected computers are
referred to as "Zombies" in the industry. Zombies
have an "smtp engine" like the spammer programs and
send out spam the same way, by connecting directly
to the recipient's mail server.
The current Zombie programs can not send out spam if
Port 25 is blocked. If Zombie operators update their
programming to use the ISP's outbound mail server,
then the Zombie machines will be easier to identify
and block.
|
| More Information and References |
|
Blocking Port 25 Traffic
'MyDoom' virus reheats the discussion
http://www.broadbandreports.com/shownews/38004 BellSouth Blocking Port 25
Not clearly informing customers
http://www.broadbandreports.com/shownews/43478 |
|
|
