Helping people with computers... one answer at a time.

For various reasons I have two email accounts with different ISP's ... Comcast and Verizon. For some reason when I'm at home, where Verizon provides my connectivity, I can't send email using my Comcast account. Yet when I'm at work or elsewhere, I can send using either. Why? And what can I do?

Welcome to another casualty in the war against spam. ISPs are starting to use various techniques to limit the use of their mail servers to only their clients.

Depending on what your ISP allows, you may be able to reconfigure. On the other hand, while it wasn't the last straw, it's one additional reason that my former ISP is my former ISP.

The techniques ISPs use fall into a few buckets:

  • They may only accept mail for sending if you are connected to their mail servers on their network. For example only if you are connected via the dialup or DSL connection that they provided you.
  • They may only accept mail for sending if the "From" address is on a domain that the ISP hosts.
  • They might intercept attempts to send mail through other mail servers, and redirect through their own - and them impose restrictions.
  • They might require a separate login in order to send email.
"With all those possibilities, and with all the possible ISP combinations, it's difficult to present The Answer."

There are probably other techniques in use as well.

I'm going to assume from the question that you can receive email on both accounts, so I'll limit myself to sending issues. With all those possibilities, and with all the possible ISP combinations, it's difficult to present The Answer. But I can at least go over a couple of things that I'd try.

The normal configuration might be to have each account send email using the SMTP server provided by that account's ISP - by that I mean your Verizon mail account will use Verizon's SMTP server, and the Comcast account would use the Comcast server. Instead, try configuring the problem account to use the other accounts SMTP server.

For many years sending email via SMTP required no authentication. Especially when you're connected via the ISP's provided lines such as dialup or broadband, that was enough to "authenticate" that you are authorized to use the ISP's servers. Many still operate that way by default but impose some simple restrictions such as requiring that the "from" address be something that the ISP controls. Quite often the ISP will lift restrictions as long as SMTP authorization has been successfully used. Try configuring the account that's not working to use authentication - either "same as receiving account", if that's an option, or with explicit account/password information.

And it's even worth combining those two approaches: try sending using the "other" accounts mail server, and try adding authentication to that configuration as well.

If efforts so far have been unsuccessful, it might be worth asking one of your ISPs if they even support what you are doing. Some might allow you to send using a different port - something other than the SMTP standard port 25 - or they might have alternate approaches. Or they might not help at all, and you'll know it's time to find another ISP.

Article C2523 - January 17, 2006 « »

Leo Leo A. Notenboom has been playing with computers since he was required to take a programming class in 1976. An 18 year career as a programmer at Microsoft soon followed. After "retiring" in 2001, Leo started Ask Leo! in 2003 as a place for answers to common computer and technical questions. More about Leo.

Not what you needed?

Greg Bulmash
January 22, 2006 6:21 AM

I'd say the solution is to run your own SMTP server locally and sidestep your ISP's SMTP altogether. I did that for a while in the '90s when I was a PacBell DSL customer and their SMTP servers kept crashing.

Unfortunately, many viruses and spambots use their own SMTP servers, as do real live spammers, meaning a number of ISPs are blocking port 25 traffic (the SMTP port) to combat spews of spam and virus-infected mail coming from infected PCs on their networks.

This is done to force you to use their outbound mail servers. Realize, though, that most don't require you to use your ISP username or e-mail address in the "From" line, so you can still send mail that appears to be from your Verizon account through the Comcast SMTP server.

Currently I have Mozilla Thunderbird picking up POP or IMAP mail for 15 different e-mail addresses through 4 servers, but I can answer all that mail from home and send it out via my Comcast SMTP server.

The only place this becomes difficult is when I'm on the road with my laptop. But my web host provides SMTP services (with login required), so I can send mail for most of my accounts so long as I have internet access.

- Greg

deborah dobson
March 1, 2006 4:33 AM

i need to know is my comcast e-mail activated i also have a yahoo e-mail but i want to use my comcast as well

Jack Harding
April 11, 2006 11:35 AM

after trouble shooting Outlook error 0x80042109! I found that comcast has taken filtering of spam to a new level at the modem by turning off port 25 completely. There is a boot file in the modem that turns off the port. You must contact Comcast Abuse representives to turn it back on!

Matt Brooks
April 21, 2006 8:08 PM

Jack, I contacted Comcast, but they insist port 25 is not blocked for me, even though this is the last possible solution! It is SOOOO frustrating. There is no way to contact their Abuse people other than email. Their phone number just gives a voice message saying to email them. Do you have a trick on getting the solution expedited?

August 4, 2006 6:58 PM

i cannot recieve or send e-mail please help me

September 19, 2006 7:04 AM

Why can't the people in my addressbook with COMCAST address receive my mail?? Is it my problem or theirs??

Leo Atkinson
September 25, 2006 9:14 PM

Hi Leo, it's Leo just wondering if you know why I can't send a link from IE 6 to my own Email address?.This function of IE only failed after downloading (auto)WGA file(KB905474).So much for Win auto updates,I can't wait till someone comes up with a viable windows alternative.
I asked you because all us Leo's are smart and that's not a biased opinion.
Regards Leo

October 10, 2006 4:00 AM

why everytime i try to send emails to people on msn my yahoo keeps telling me that there is a permanant error what it that about.

Leo A. Notenboom
October 10, 2006 9:13 AM

Depends on the rest of the error message.

November 14, 2006 2:54 PM

just movement before when i write mail & i can send eassly. but right now i can't write any thing inside my folder because i want send mail to my friend.

November 21, 2006 6:17 AM

I cannot send email in outlook express, i can recieve email the email comes back bounced by administrator - I called my ISP and they say it' not their problem. Can you help
The email comes back from - is this a virus??


January 22, 2007 11:36 AM

why cant i use my email from verizon through outlook

February 11, 2007 12:04 PM

Hi Leo,

How can I read my comcast & yahoo emails through outlook? Does this possibility exists?


March 6, 2007 7:41 PM

i cant send and receive email. what will i do? i've made a lot of email address butn it seems the same problem.

March 21, 2007 9:13 AM

on my qwest msn,i can receive e-mails,but i cant send

Leo Notenboom
March 22, 2007 2:48 PM

Hash: SHA1

No way to know without knowing what happens when you try. Errors? No errors?
Mail stays in outbox? Leaves outbox? Need more details.

Version: GnuPG v1.4.6 (MingW32)


May 17, 2007 8:10 AM

I used to be able to get into my hotmail accounts by clicking on the OPEN YOUR EMAIL IN-BOX 'letter' on my MSN MESSENGER. With the latest version it opens a blank page with ERROR on the left hand bottom.
I prefer to go back to the previous version .....

Miep Visser
[Email Address Removed]

Pete Duncan
July 15, 2007 2:19 PM

I just stumbled across a solution to a problem my mother-in-law was having after Comcast took over her Roadrunner account. In the Outgoing Server (SMTP) settings, I had to change her username to ALL CAPS. the original username "" (not her real address) now needs to be " (I didn't check to see if the "H" in Houston really needs to be in caps.) She can still receive emails that are addressed to the lowercase name, but she could not send mail until the "new" uppercase name was entered in the SMTP settings of her email program.

September 30, 2007 7:30 PM

why can't i send out email through my yahoo email address?

benjamin goldenbloome
October 17, 2007 3:09 AM

it won't let me send an email no matter how many yahoo accounts i create ,,it just keeps blanking the page and the email never goes out and it never changes the page it just keeps the same page,,,almost like someone is preventing me from sending an email,,,i can go to the libary's computer and send an email but when i get home it won't go out,,,it is a back door virus,,,i bought the NORTON buisness edtion the expensive on for almost 300.00,,,,please help me

Chris Carpenter
November 14, 2007 9:44 AM

I read your article but I still cannot figure it out, (my problem), I have checked all the settings, (same as always), the Verizon in Outlook can rec. but cannot send. Its says it is sending but the intended recipient never gets the message. It appears in the sent file, send/rec. produces no error messages, i have deleted the account and reentered the info. I aam at a loss. Verizon reset the password but that didn't help.

Walter Thorn
November 28, 2007 9:37 AM

Neither I nor my wife, Marlyn Thorn, [email address removed], are able to compose, reply, or forward our emails! Please fix this problem!

Janet Russell
January 23, 2008 4:09 AM

I send emails of my updates of events to my own email so I can forward it on to my email list and for some reason it keeps saying that I cannot send or recieve emails I dont know what I am doing wrong please help me thanks Janet

May 14, 2008 12:47 PM

frankly speakin,i just dont know how to send an e-mail via my e-mail account.Plz help.i,ll be grateful

August 6, 2008 10:01 PM

why cant' i send emails on my account (its and aol account and i am using aol v. 9.0) when i click the send mail icon it says "sending mail is not permited with this account" thank you for your help in advance

Susan Reyes
August 23, 2008 10:50 PM

why can't i send any messages (forwarded, compose & reply) to [email address removed]? Only her account is always a failure. The rest of those in my contacts receive messages from me.

Depends on the specific failure and error message. Double check you have the email address correct.


M Current
October 31, 2008 6:59 AM

Leo -

Thanks a TON! I was able to adjust my Outgoing Mail Server Options to match the settings of my incoming mail server...AND IT WORKED!


tiffany ruffin
November 19, 2008 1:35 PM

when I try to send an email through my yahoo account it just keep saying loading and never loads.

January 3, 2009 3:19 PM


January 28, 2009 6:20 AM

I cant send mail from my yahoo account!! When i send it states mail sent but the receipt wont rcv it and it wont appear in the sent items. Plse fix it, its been happening for a month now

Gary Albertson
February 18, 2009 7:33 PM

hope you can help. i am onvista and sometimes when i go to a site to send in (a contact us} prompt, i get this display from windows that it no longer allows HTTP. it offers a fix, but i have tried several times to comply but no-go. i previously had hotmail and changed to yahoo hoping it might help..nope. thanx for any input.

March 6, 2009 9:09 PM

when I try to send an email through my yahoo account it just keep saying loading and never loads.
then direct "comt" error send/not send ..and when I klick don't send everything Disapear..

Phil Smith
March 10, 2009 2:15 PM

All of a sudden, I am unable to send any semblence of a large email size (above 49kb)using Windows Mail (Vista) and with Comcast. Internet is fine and I can receive just about any size email.
Usually get an error 0x00CCC0F. Have tried Thunderbird and same problem.
need help!

March 22, 2009 10:03 PM

my problem is i cant compose any mail from my emailid

April 9, 2009 3:53 PM

i cant send pic from my yahoo accont

joe fiebert
April 10, 2009 9:24 PM

I can't send email to my aol address from my cell.All the other addresses from yahoo and comcast work o.k.I can even sen an email from my mobile yahoo to my aol email but can't send directly from my cell phone to aol.Please help!!

May 17, 2009 11:14 AM

cant sent emails. they keep coming back as a failure

August 13, 2009 4:37 AM

the email page won't allow me to compose/send email for the past two weeks help

September 6, 2009 10:32 AM

cant send emails they keep comeing back as failurei have two accounts google&yahoo

The error message you're getting back should include a reason.

amanda richardson
September 11, 2009 8:51 AM

i cannot send email-i can forward, reply, etc-i just cant send email-this is the 2nd day

judi fermanich
November 16, 2009 9:11 AM

This "improvement" has cost me access to my accounts and is in no way an improvement for me. I hate it and want my accounts reestablished or I am out of here. Do not fix things without notifying members that you are doing so. That is bull..... And making it harder to reestablish these accounts is ludicris at best. Thanks for nothing! I am not savvy enough to do the things you suggested and why should I have to? You screwed it up, now fix it!

For the record I am not your ISP, and I'm not making these decisions. Complaining here actually does little to no good. Contact your ISP.

Larry Larson
February 28, 2010 4:11 PM

If you are traveling, a lot of times the ISP will only allow access to their own SMTP servers, but you may not know what those SMTP servers are. The best solution is to have an authenticated 3rd-party SMTP server that allows you to send email from any ISP on an alternate port (for example port 587). A good service like that is

March 16, 2010 5:02 AM

can't send e-mail from my account,,i receive but i can't write text,,,or reply,,,thanks

March 18, 2010 9:57 PM

i cant send any mail since one week

lynn cox smith
June 13, 2010 7:07 AM

i cant send no email from my face book i have not done thaing fix thank you im upset

MIchael W
July 22, 2010 10:01 AM

I've found that SMTP client sends are a perpetual problem.

You can see Corp Doctorow talking about it, too, at

All these approaches work -- more or less. But the most-reliable thing I've found to do is a little tool by Loa Corporation at

It's a tiny little local server you put on your hard drive. You sign up for a Loa account, then point all your mail accounts at your local server, and just let it run. The Loa local server collaborates with Loa's infrastructure to send out your email, and it works just about everywhere.

I've been using it for the last 2 years and outgoing SMTP mail issues are thing of the past.

March 6, 2011 2:26 PM

Just thought I would share this, you can check if your ISP is blocking outbound port 25 at

November 20, 2011 3:11 PM

Why does my ISP "South Central Communications" block all my outgoing emails to my own address list? (ie: by the ccc69 error in outlook express) They have told me before they did it. But why? I spend good money I give them on my account so I should be able to send my own emails out to my own buddies.

November 20, 2011 5:06 PM

You should ask your ISP why they are blocking you and how you can solve the problem with them. There are specific rules and laws around sending large amounts of email. They should be able to help guide you towards getting in compliance.

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