If you cannot send email through Optimum Online (Optonline) or another Internet Service Providers (ISPs) 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 your web host or 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.

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

  • 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.
    Bower Web Solutions recommends that all of it’s clients use port 587.
  • If you cannot use port 587 and you don’t want to change to Bower Web Solutions hosting:
    Change outgoing mail server to your ISP’s:
    You can change your OUTGOING mail server (SMTP) from “mail.yourdomain.com” or “yourdomain.com” to a SMTP mail server provided by your ISP.
  • 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!


  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.
  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

Problems Sending E-Mail Using Optimum Online or SMTP Settings for Optonline and other ISPs

If Your Internet Service Provider (ISP)
or Phone Carrier is:
Your STMP Server or “Outgoing Mail Server”
Address would be:
Adelphia mail.adelphia.net
America Online (AOL) smtp.aol.com
Atlantic Broadband smtp.atlanticbb.net
AT&T (Broadband) mail.attbi.com
AT&T (Dialup) smtp1.attglobal.net
AT&T Worldnet mailhost.worldnet.att.net or imailhost.worldnet.att.net
BCPL mail.bcpl.net
Bellatlantic gtei.bellatlantic.net or smtpout.verizon.net
Bellatlantic.net smtpout.bellatlantic.net
Bellsouth mail.bellsouth.net
Bestweb smtp.bestweb.net
Blazenet smtp.blazenet.net
Cable One mail.cableone.net
CAIS smtp.cais.net
CAPU smtp.capu.net
Charm.net smtp.charm.net
Charter Communications smtp.charter.net
Comcast smtp.comcast.net
Compuserve smtp.compuserve.com or smtp.site1.csi.com
Concentric.net smtp.concentric.net
Covad smtp.covad.net
Cox West smtp.west.cox.net (west coast users)
Cox Central smtp.central.cox.net (central users)
Cox East smtp.east.cox.net (east coast users)
Cox Business smarthost.coxmail.com
Crosslink smtp.crosslink.net
DCANET smtp-relay.dca.net
Delmarva Online mail-gw.dmv.com
Delta Net smtp.deltanet.com
Direcway smtp.direcway.com
DSL Extreme smtp.dslextreme.com
Earthlink Network mail.earthlink.net or smtp.earthlink.net
Earthlink Network (International only) ismtp.earthlink.net
Edge.net mail.edge.net
Enter smtp.enter.net
EROLS mail.erols.com
Ezy smtp.ezy.net
Flashcom mail.flashcom.net or smtp.flashcom.net
Frontline.net smtp.fcc.net
Gateway.net smtp.Gateway.net
GTI mail.gti.net
HotMail mail.hotmail.com
IBM.Global net smtp1.ibm.net
ioNet Inc mail.ionet.net
Interaccess.com smtp.interaccess.com
Internet America mail.airmail.net
ITOL mail.itol.com
Juno smtp.juno.com
Mediacom mail.mchsi.com
Mediaone.net smtp.ce.medione.net
MegaPath mail.megapathdsl.net
MCI mailrelay.mciworldcom.net or mailrelay.internetmci.com
Mindspring smtp.mindspring.com
MSN smtp.email.msn.com
Nauticom mail.nauticom.net
Netcom smtp.ix.netcom.com
Netcom (Canada) smtp.netcom.ca
Netscape smtp.isp.netscape.com
NetZero smtp.netzero.net
NYU.edu smtp.nyu.edu
OLG.com mail.olg.com
Optimum Online Internet Service (optonline) mail.optonline.net
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.
Pacbell mail.pacbell.net
Patriot Media smtp.patmedia.net
Pipeline smtp.pipeline.com
Prodigy smtp.prodigy.net
PSI.net relay.smtp.psi.net
PTD.net promail.ptd.net port 25
QIS mail.qis.net
Qwest Internet Service pop.dnvr.qwest.net
RCN smtp.rcn.com
Rider.edu enigma.rider.edu
RoadRunner smtp-server.<your-region> .rr.com
SBC Global smtp.sbcglobal.net
SBC Global Yahoo smtp.sbcglobal.yahoo.com
Smallville Communications mail.toto.net
SNiP mail.snip.net
Spectrum DSL mail.webstable.com
SprintLink smtp.a001.sprintmail.com
Sprynet m6.sprynet.com
Starpower smtp.starpower.net
Sympatico mailhost.sk.sympatico.ca
UMBC smtp.gl.umbc.edu
USA.NET mail.netaddress.usa.net
US Internet smtp.usit.net
UUNet mail.uu.net
Verizon Internet Services outgoing.verizon.net or smtpout.verizon.net
Verizon may require the use of port 587
to send outgoing mail as well.
Wide Open West smtp.mail.wideopenwest.com
XO Communications mail.njd.xo.com or smtp.concentric.net
Yahoo smtp.mail.yahoo.com
Ziplink smtp.ziplink.net