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Problems Sending E-Mail Using Optimum Online (Optonline) or Other Internet Service Providers (ISPs)

UPDATED: June 25, 2012

If you cannot send email through Optonline or another ISP and you are receiving an error message which states something such as "Cannot send outgoing mail due to Port 25 being blocked", this usually indicates a problem with your Internet Service Provider (ISP) and NOT Bower Web Solutions itself.

What Is Port 25 and why is it being blocked?

To help control the amount of spam and viruses that originate from your ISP (like Optimum Online or Earthlink, etc.) your Internet Service Provider may start to implement outbound Port 25 (SMPT) filtering. Filtering Port 25 is a common spam control measure used by Internet Service Providers and the advantages far outweigh the disadvantages when it comes to the war on spam. However, these efforts will not necessarily protect yourself from being flooded with spam. To protect your e-mail account from spam, we suggest you take a look at our E-mail Defense Service.

How can I send my e-mail if my ISP is blocking Port 25?

  • Change outgoing mail server to your ISP's: You can change your OUTGOING mail server (SMTP) from "" or "" to a SMTP mail server provided by your ISP.
  • Send via Port 587: Many ISP's (including the two biggest in Northern New Jersey and the New York City Metro area, Verizon and Optonline) allow you to send e-mail using your outgoing account through Port 587. Sending through Port 587 is especially convenient for laptop users who use multiple ISPs. Learn how to send via port 587.
  • For more information on why Port 25 may be blocked, try visiting the Verizon website or the Optimum Online website.

See the list below of leading Internet Service Providers and
their Corresponding SMTP (Simple Mail Transfer Protocol) or "Outgoing Mail Server" settings


For example, Optimum Online now require their internet customers use the following SMTP mail server to send out mail on their network:

If you already have your e-mail program (such as Microsoft Outlook, Mac Mail, etc) you do not need to recreate your e-mail account information again. You simply need to edit the existing account and change the SMTP server for the account(s). After you have entered your IPS's SMTP server, you will will then need to click on the 'more settings" tab and go to the "Outgoing Server" tab. On this tab, click on the "Log on using" radio button and enter your user name and password AS PROVIDED BY YOUR INTERNET SERVICE PROVIDER or ISP. (Note: this is NOT your Bower Web Solutions user ID and password).

Be aware that many Internet Service Providers (ISP) such as Optimum Online, Verizon, Comcast are now cracking down of "spam activity". These ISPs are now limiting how many e-mails you can send out from your computer's location within a given time period and may suspend your ability to send e-mail if you are sending more than 30 recipients at a time or more than 50 separate e-mails within an hour.

If you plan to send large numbers of mass e-mails to your client base, you really need to consider a separate service such as Constant Contact. For less than 75 cents a day, you can take advantage of advanced e-mail tracking features and sleep at night know that your web site or web server will not be "blacklisted" by the major ISPs!

Click the image below to get your FREE Constant Contact account!

FREE Email newsletter from Constant Contact

Below is an example of changing an existing Outlook e-mail account configuration using Optimum Online as an ISP:

  1. Go to the Tools menu and choose "Accounts..."
  2. From the Mail tab, choose your e-mail account and click the "Properties" or "Change" button
  3. In the following window, click on the Servers tab
  4. Change the Outgoing mail (SMTP) server setting to:
    Note: If your ISP is NOT Optimum Online, then you will need to set your SMTP to a different server. Please contact your ISP directly for more details.
  5. Finally click on the "More Settings" button and enter your ISP username/password in the "Log on Using" section. (see illustration below).

    Internet E-mail settings
  6. Test account Settings (from the general tab or by clicking OK to return to the main window).
  7. If you get the error "None of the authentication methods supported by this client are supported by your server", uncheck my outgoing server requires authentication. As of early 2009, OptOnline was not requiring that you sign into an account, but merely that you send out using their outgoing mail server.

List of Internet Service Providers and Their Respective SMTP or Outgoing Mail Server Settings

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NOTE: This list is provided as a courtesy to our customers. As different ISPs change their system configurations, we cannot guarantee complete accuracy with the list below. Please contact your ISP or visit the Support sections of their respective web sites for the most accurate and up to date SMTP settings as required by your Internet Service Provider.

If Your Internet Service Provider (ISP)
or Phone Carrier is:
Your STMP Server or "Outgoing Mail Server"
Address would be:
America Online (AOL)
Atlantic Broadband
AT&T (Broadband)
AT&T (Dialup)

AT&T Worldnet or
Bellatlantic or
Cable One
Charter Communications
Compuserve or
Cox West (west coast users)
Cox Central (central users)
Cox East (east coast users)
Cox Business
Delmarva Online
Delta Net
DSL Extreme
Earthlink Network or
Earthlink Network (International only)
Flashcom or
IBM.Global net
ioNet Inc
Internet America
MCI or
Netcom (Canada)
Optimum Online Internet Service (optonline)
  As of early 2010, OptOnline was not requiring that you sign into an account, but merely that you send out using their outgoing mail server. If when testing e-mail settings (in Outlook) you get the error "None of the authentication methods supported by this client are supported by your server" uncheck my outgoing server requires authentication.
Patriot Media
Prodigy port 25
Qwest Internet Service
RoadRunner smtp-server.<your-region>
SBC Global
SBC Global Yahoo
Smallville Communications
Spectrum DSL
US Internet
Verizon Internet Services or
Verizon may require the use of port 587
to send outgoing mail as well.
Wide Open West
XO Communications or