Windows 10 Mail (the native Outlook Mail app) won't send via SMTP

Xerostomia said:

When windows upgrades and 'imports' all my settings from windows 8.1, the mail app recognizes the old cox settings and only asked for my password and everything got filled in perfectly. In the two computers where I had to manually input the IMAP and SMTP settings it does not work, even though the settings are exactly the same.

I do not even know where to start looking at what is the difference between them, but I think the problem is not in the mail app itself, but in some sort of setting (maybe a firewall setting?)

It is a known issue with the Windows 10 mail app.  Microsoft removed the ability to enter the SMTP port when configuring the account.  This issues effects other ISP's too, not just Cox.  As I said previous, I use Thunderbird and have no problems with Windows 10 ... that's a solution for a PC but doesn't help Windows phone users.

That may be so, Tiffany.  I don't use it so no first hand experience.

FWIW...

My problem with the Windows 10 email client is I can't even get to the point of inserting port information at the end of the server addresses. When I go to add my Cox email address I simply get an error message saying We can't find info for that account. Make sure the email address is correct and try again. I do not get a chance to enter the advanced settings.

Please note I do normally use Outlook 2010 on my Win 10 laptop and that works just fine.

Interestingly the newly updated iOS Outlook apps for the iPad and iPhone would allow me to select the advanced settings and append the port information at the end of the server addresses, ie. imap.cox.net:993 and smtp.cox.net:465. Subsequently I can both send and receive email using my Cox address on the iPad and iPhone with the Outlook for iOS app.

Becky,

Thanks for your honesty.  I'm having the same problem.  Can't send my cox email in Windows 10.

 I found the posting below, with a possible solution,  in a Microsoft forum. 

 Does it make any sense to you (or anyone else)?

"This problem is not limited to comcast/cox - I've got the same issue with another provider.

After getting in contact with my ISP they investigated a bit and found that the HELO/EHLO entry that the Mail App passes to the server doesn't 100% conform  RFC specs.

-------------------------------------------------------------------------------

Excerpt of Server log:

550-[IPv6::::192.168.###.###]  
550-This is commonly associated with misconfigured mail software: 
550-please see RFC2821 for legal domain syntax. 

H=([IPv6:::ffff:192.168.###.###]) [###.###.###.###] I=[###.###.###.###]:25 
F=<mail@server.com> rejected RCPT *** Email address is removed for privacy ***>: 
rejected due to unacceptable syntax in EHLO/HELO name: 
[IPv6:::ffff:192.168.###.###] 

-------------------------------------------------------------------------------

 By adapting to server settings to allow for these deviations they got it to work for me again."

In Windows 10 Mail app, SMTP appears to be hard coded to use port 587 (110 for POP). So, the port number defined in Cox Email Server Names at:
http://www.cox.com/residential/support/internet/article.cox?articleId=a8fb24c0-6440-11df-ccef-000000000000
are unattainable from Windows 10 Mail. Maybe through a registry hack, but not through the settings user interface.
 
Port 465 is obsoleted and Cox should probably transition to supporting port 25 or 587 for smtp.

In the mean time, I've found using smtp.cox.net:25 to use port 25 is allowing sends (TSL?) even though other functions may be limited.

While Cox and Microsoft duke it out, we'll be forced to use other mail clients to access Cox mail servers. Share this and any other news about the situation so that other confused W10 newbies like me don't waste more time. I'll buy the first one who finds a solution to this a cup of coffee!

There is definitely something other than the port at issue. I checked Windows Firewall logs sending e-mails using both Windows Mail and Thunderbird. As long as you have the outgoing authentication and SSL boxes checked in Mail, both send the mail using port 465.

JohnD

Windows 10 has been out for nearly two months and we still cannot send an email from a Cox account using the native Mail app. This is completely unacceptable. One would think by now that two big companies like Cox and Microsoft would be able to get together and resolve this critical issue. Apparently not.

Essentially, anyone using Windows 10 native Mail app with a Cox account is unable to send email. For those of us using tablets, adding the extra overhead and SSD space of a third party email client like Thunderbird is NOT a viable option.

Cox, you have had more than a year of access to Windows 10 prior to release. Get your act together, figure it out, and make it work. NOW!

Since it doesn't look like COX and Microsoft are going to fix this anytime soon, what are the options?   Change to a different service provider?  Is there a way to uninstall 10 and go back to an earlier version that's compatible with Cox email?

Hi Everyone,

This was a common problem after the release of Windows 10, and it affected many ISPs. From researching other sources, it appears that the Microsoft Windows Resource Checker Tool (also called System File Checker) often fixes this issue. This tool scans and verifies the integrity of all protected system files and replaces incorrect versions with correct versions. You might want to contact Microsoft Help for further assistance at https://support.microsoft.com.