Support from Internet Connection

Recent Mail-sending Problems

Sent: 2004/08/17
Audience: All Hosting Customers.

Over the past couple of days, many customers, especially customers who use Comcast to connect to the Internet, have noticed problems sending email. All of these problems are due in one way or another to spam.

- First, Comcast and other ISPs have been blocking access to port 25 on any network but their own. As more and more ISPs adopt this practice, we expect to have more customers experience mail-sending problems.

- Second, we have subscribed to some additional RBLs, Real-time Blackhole Lists. These lists, also know as blacklists, contain IP addresses that spam has originated from. Our network has subscribed to many RBLs for some time now and realized a great reduction in spam traffic because of them. These additional lists will further help us to reduce the amount of spam traffic on our network, and in your Inbox.


Customers being effected by the first issue are commonly getting a "Connection Refused" error when attempting to send mail through the SMTP service we provide. If your mail client is configured to send mail through "" or "" and you are getting this error, your ISP is probably blocking your access to port 25 on our network. To test this without sending mail, you can telnet to port 25 on or
If you see "connection refused" then your ISP is blocking this port.

To avoid this problem, either configure your mail client to use the SMTP server provided by your ISP, or to use an alternate SMTP port that we provide, port 587.

Some SMTP server addresses for ISPs:

Comcast -
Earthlink -
SafePages -
SurfBest -
Mediaone -*
  *Note: Replace "se" with your Service Area (e.g. "ne" for New England)
Mindspring -
NetZero -
Prodigy -
RoadRunner -*
  *Note: Replace "se" with your Service Area (e.g. "cinci" for Cincinnati)

To change your mail client's settings to use our alternate SMTP port, please follow the directions below.

For those of you who are using Outlook Express, you can change your SMTP port by following these steps:
1. Go to the Tools menu and select Accounts.
2. Select your email account from the list and then click the Properties button.
3. Under the Advanced tab, look for SMTP port 25 and change it to 587.

On Mozilla Thunderbird, the process to change SMTP port 25 to 587 is as follows:
1. Go to the Tools menu and select Account Settings.
2. Select Outgoing Server (SMTP) from the list on the left.
3. Find the box marked "Port:" and enter 587.

If you aren't using Outlook/Outlook Express or Mozilla Firebird, we will have additional instructions in our support area shortly. In the meantime, you can contact the support desk for specific instructions for your email client.


Errors related to the second mail-sending problem, our recent subscription to more RBLs, often results in the mail user receiving a "451 Blocked" error. If you get this error your ISP or IP address has been submitted to one or more RBLs. There are many reasons why an ISP IP address would be submitted. Another customer of your ISP might have sent spam email, you or another customer using that IP address might have had a virus, etc. For instructions on how to check if your ISP or IP address is blacklisted, please visit this page:

More info on Blacklists. Checking if you are Blacklisted.

For the most part, after today, customers should no longer have any trouble sending mail through our network even if their ISP or IP address is blacklisted. Slight changes made to our system today have allowed blacklisted users to send mail if they use SMTP authentication.
Still, blacklisted customers should take the steps necessary to remove themselves from any RBLs they are on.

If your ISP or IP address has been blacklisted and you continue to have trouble sending email through our SMTP service, please ensure that your email client is configured to use SMTP authentication. This document discusses how to set up this feature:

SMTP Errors


Overall, the changes we have made to our mail-sending services have not "broken" anything as it may have appeared. These SMTP problems are the direct result of Spam becoming more pervasive and various Internet providers updating their software and their policies in an effort to combat it. Any issues directly related to changes made to our network, namely subscribing our network to additional RBLs, have only revealed already-existing problems, i.e. that your ISP or IP addresswas blacklisted.

AS for the decision to subscribe to more RBLs, it was made in your best interest. Afterall, the greatest single complaint we hear most from our customers is about spam. By developing products such as the SVFilter and instituting policies and practices such as the subscription of RBLs, we have reduced the amount of spam on our network and in your mailboxes.

We appreciate your feedback and welcome your questions and comments about this issue. Please feel free to contact the Internet Connection Support Desk through these means:

Phone: 410-820-5678
Toll Free (US resellers only): 800-203-5678 2004-2005 ©