Outlook 2016 will send a test message, but not a composed message

Greetings wise wizards of EE:

I'm helping a friend who recently purchased a copy of Microsoft Office Home and Business 2016, and needs Outlook set up for her Yahoo business account.

I first used the default "simplified account creation"  set up with Outlook (which I truly despise, as it does not permit access to the server settings), and though she could receive, she could not send messages. The message she compose would just sit in the Outbox, with no error message being generated.

I then used the "disable simplified account creation" registry edit that Microsoft publishes: https://support.microsoft.com/en-us/help/3189194/how-to-disable-simplified-account-creation-in-outlook , which DID work, and permitted me access to the server settings.

Then I discovered something very odd... I inputted the correct server settings, and successfully TESTED the ability to receive and SEND, which passed. Though I can send a Microsoft Outlook test message successfully, Outlook will not send a composed e-mail message.

I am at a loss, and Google searches did not help. Any advice or suggestions would be most welcome indeed.

Many thanks in advance,

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Jose Gabriel Ortega CastroEE Solution Guide/Topic Advisor and CEO Faru Bonon ITCommented:
Did you try to use this settings?
Source: https://help.yahoo.com/kb/SLN4724.html 

Incoming Mail (POP) Server

Server - pop.mail.yahoo.com
Port - 995
Requires SSL - Yes
Outgoing Mail (SMTP) Server

Server - smtp.mail.yahoo.com
Port - 465 or 587
Requires SSL - Yes
Requires TLS - Yes (if available)
Requires authentication - Yes
Your login info

Email address - Your full email address (name@domain.com.)
Password - Your account's password.
Requires authentication - Yes
zovothAuthor Commented:
Greetings Jose:

Many thanks for your response, but POP settings are not the solution I am looking for... POP is the older of client mail format, and does not sync with multiple devices... meaning that my friend would have to manually delete messages on the computer as well as her smart phone, and their would be only a record of sent messages on the one device that sent it... I must find a solution using IMAP, which will sync with the inbox, sent folder, any custom folders, etc.

I appreciate the suggestion though, but troubleshooting this odd IMAP situation is what I am after.

Davis McCarnOwnerCommented:
Is it a true @yahoo.com email address or one of the migrated ones (eg @bellsouth.net or @sbcglobal.net)?
If it is the latter, you need to login to the account management site and generate a "secure password".
P.S. I have had to deal with this problem repeatedly since August.
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zovothAuthor Commented:
Greetings Davis:

DOH! I neglected to say it is not @yahoo.com email address, but rather a Yahoo hosted e-mail address for a business, with a custom domain... how foolish of me... I think you are on the right track... I will visit the e-mail control panel for this account and generate the secure password as you suggest.... now that I think about it, that makes perfect sense.

Thanks so much for the suggestion, I'll check back on this post in a day or so and let you know what the results were.

Davis McCarnOwnerCommented:
Custom Domains may not need a "secure Password"; but, they definitely do use different servers and authentication.  Check those while you are on the site.

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zovothAuthor Commented:
Greetings Davis:

Many thanks for the helpful suggestions regarding the custom domain Yahoo e-mail Outlook issue. Your suggestion was definitely in the ball park... it turned out to be that the two-factor authentication was turned on in the security section of the Yahoo account profile. Once I turned that off, the account worked without issue.

Your suggestion is what inspired me to look in the right spot, so I thank you for your assistance!

May the wind be at your back,

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