hotmail refusing to accept e-mails from talktalk

[LindaK2]

For the last month or so, any e-mails I send to a friend who uses Hotmail are being rejected, with return message saying it has been refused by Hotmail -

host eur.olc.protection.outlook.com[52.101.68.24]

    said: 550 5.7.515 Access denied, sending domain TALKTALK.NET doesn't meet

    the required authentication level. The sender's domain in the 5322.From

    address doesn't meet the authentication requirements defined for the

    sender.

. This only happens when I send via Outlook - if I send direct from my TalkTalk mail it's okay. Any suggestions please? 

[mandisa1-TT]

Thank you so much for the information @nameunknown_ 

Hi there @LindaK2 We apologize for the inconvenience caused to you, however as you have confirmed webmail is working correctly, hopefully the issue with third party app will be resolved soon:)

[LindaK2]

Yes, I suspect this issue will go away too, as a few months ago it was Sky that wasn't accepting TalkTalk messages, and that was resolved without me having to do anything. So annoying though. 

Not sure what version of Outlook I'm using but I think it's the most up to date one.

[nameunknown_]

@LindaK2 

You ought to be able to use third party applications. What @sabelo-TT is saying is that TalkTalk don't provide support for any issues you have when using third party applications, and recommend you use webmail instead.

For some reason your email is failing the strict authentication checks that Microsoft is now applying.

The other day I was assisting someone who had the same issue here:

https://community.talktalk.co.uk/t5/Email/TalkTalk-Email-Sending-Errors-to-Microsoft-Emails/m-p/3128...

The issue went away without the user making any changes, or identifying the cause. 

Although the issue is occurring when using a third party application, I doubt that the third application is at fault.

I think the person I was assisting was using Microsoft Outlook 2019. What version of Outlook are you using?

[LindaK2]

My e-mails have always gone via Outlook but it's only very recently that I have been having this problem. Is it something new that 3rd party apps are not supported?

[Billx]

I don't think many would be able to answer this.

There has recently been a new development.

Now these big email service providers are checking 2 domains of the sender, the domain of the 5322.From email address

and the domain of the 5321.From email address. These refer to RFC 5321 and RFC 5322.

[sabelo-TT]

Hello there @LindaK2, you have stated that when trying to send via TalkTalk webmail, you are able to send the email however when in use of the outlook App, you are not able to send. 

We do suggest continuing to send all email via TalkTalk webmail as 3rd party Apps are not supported.