I suggest chatting with onetel. It is highly probably that they have changed either some DNS information or even the routing of their SMTP server that has caused this. Perhaps even changing the SMTP server used for web mail and recording only that in DNS as an approved sender.

Many providers like Google and Yahoo bounce messages or drop connections from unknown servers, working on the theory if it is not spam, then the connection will be repeated many times. How many times depends on the reputation of the sending server.

Thanks for replying. I only recently found out he's been using the btinternet.smtp for his onetel address as he had issues with onetel.smtp many years ago.

I read that The Carphone Warehouse's TalkTalk brand own Onetel and then found this post for someone having sending issues :

"Are you a TalkTalk broadband customer? The reason for asking is that you'll need TalkTalk network authentication to be able to send emails.

Have you had any incoming emails to the onetel email address from TalkTalk advising that the email account is going to be upgraded to the new TalkTalk Mail platform?so would so I'd assume he'd have to contact TalkTalk"

So you're probably right with contacting Onetel, or rather Talk Talk, and see what's going on there. But if he's been using the smtp.btinternet, why would any Onetel / TalkTalk issues affect sending?

lets see, for an example.

A yahoo server connects to outlook.com and says I have mail and then proceeds to drop an email for btinternet. Does that "sound" legitimate?

Then we go to onetels DNS record where the server authorised to send mail for the domain are mx1.onetel.net.uk and mx2.onetel.net.uk

See origin of that here https://mxtoolbox.com/SuperTool.aspx?action=mx%3aonetel.com&run=toolpage

So not it looks odd, and when I check the approved sender list for the domain the server connecting is not listed. But a long shot this is probably SPAM.

This what happens in the challenge and response process that is mail delivery. Unlike snail mail, the letter box slams itself if the postman is not the correct one.

I'm going to have to break this down as I don't think I fully understand.

"A yahoo server connects to outlook.com and says I have mail and then proceeds to drop an email for btinternet. Does that "sound" legitimate?" - So your saying for best functionality you need Yahoo smtp for Yahoo email and so on. Even though you may be able to mix and match some, you'll no doubt have issues.

As he made out he'd been using smtp.btinternet for his Onetel email for years, is it possible he's been getting away with it until now when TalkTalk are on the verge of 'upgrading' all Onetel addresses to TalkTalk ones. Because of this, it's causing issues like delays?

"So not it looks odd, and when I check the approved sender list for the domain the server connecting is not listed. But a long shot this is probably SPAM." - Does this mean that Onetel is not approved any more would this mean that TalkTalk are gradually replacing Onetel email to remove it entirely?

"This what happens in the challenge and response process that is mail delivery. Unlike snail mail, the letter box slams itself if the postman is not the correct one." - The email won't be accepted if the smtp (postman) is not from the same domain / server?

kirbyplonk said

I'm going to have to break this down as I don't think I fully understand. "A yahoo server connects to outlook.com and says I have mail and then proceeds to drop an email for btinternet. Does that "sound" legitimate?" - So your saying for best functionality you need Yahoo smtp for Yahoo email and so on. Even though you may be able to mix and match some, you'll no doubt have issues.

As he made out he'd been using smtp.btinternet for his Onetel email for years, is it possible he's been getting away with it until now when TalkTalk are on the verge of 'upgrading' all Onetel addresses to TalkTalk ones.

Because of this, it's causing issues like delays?

"So now it looks odd, and when I check the approved sender list for the domain the server connecting is not listed. But a long shot this is probably SPAM." - Does this mean that Onetel is not approved any more would this mean that TalkTalk are gradually replacing Onetel email to remove it entirely?

It means that when mail arrives to be delivered the server getting it checks with the DNS records that make up the glue that allows the internet to work to see if the named server is the one that should be delivering it. So if you are sending your onetel mail from yahoo the check shown it is NOT the allowed server. The allowed server has a different name.

To put it into real world. Someone knows on your door wearing a Fedex uniform and says they have a parcel for you from me. You ring me and I say not send nothing, so you go back to the Fedex man and slam the door in his face, refusing to accept the fraudulent parcel.

This is what I suspect is happening. I do not know for sure, but it is how reverse DNS works and it fits the description of the problem.

You might also want to look at this topic I am participating it as it is the same provider. https://support.mozilla.org/en-US/questions/1277019

"This what happens in the challenge and response process that is mail delivery. Unlike snail mail, the letter box slams itself if the postman is not the correct one." - The email won't be accepted if the smtp (postman) is not from the same domain / server? </blockquote>

Thanks for all the help Matt. I've learnt a fair bit. My dad put the settings back to what they were originally and it seems to be working now but unfortunately no clear answer of why.

Thanks for the link as well.

Just in case anyone wants info on Onetel server settings: https://community.talktalk.co.uk/t5/Articles/Email-settings-IMAP-amp-POP3/ta-p/2204399

Great, thanks for that. I'll pass it on in case problems arise again and he needs that to refer to.

Actually, after reading the Onetel settings from that TalkTalk link I noticed there's no SSL or Authentication. Is this just because it isn't supported or updated any more?

re :Actually, after reading the Onetel settings from that TalkTalk link I noticed there's no SSL or Authentication.

You have misread something because it states : IMAP Incoming Port 993 Incoming SSL Yes meaning Connection Security: SSL/TLS

POP Incoming Port 995 Incoming SSL Yes meaning Connection Security: SSL/TLS

Authentication Method: select “Password” or “Normal password” Do not select 'Encrypted Password'.

Outgoing SMTP Outgoing Port 587 Outgoing START/TLS Yes meaning Connection Security: STARTTLS Outgoing Authentication Yes Authentication Method: select “Password” or “Normal password” Do not select 'Encrypted Password'.

That's the TalkTalk settings though. I mean the onetel, homecall, toucansurf ones etc. from the dropdown boxes underneath.

I'm with you now....you are correct in that it uses a different port, no connection security, but you may find you need to provide the Authentication as Normal Password. The change is because it's not offered by TalkTalk for those email accounts.

Outgoing SMTP Port says 25, but a lot of servers could have issues with using that port. So you could try: Outgoing port 587 Connection Security : none

If you do not like that situation and it is understandable, then suggest you get another email address and start to inform your contacts to update their contact information to use the new email address. Your ISP should be able to provide you with an email address or you could get a free email address which is not reliant on a specific ISP eg: gmail or gmx

It's my dad's account, so I'm just worried about his security. Ideally I'd like him to abandon onetel altogether, although the change would be a hassle. I was after reasons that would convince him to change and thought having thin security on your email was reason enough to make the switch.

If it was my dad I would tell him it is not as secure and it's time to change.

You do not have to get rid of the Onetel email address immediately, just in case a few emails come through. But I would stop using it to send and get another email address that is not tied to an ISP or get a TalkTalk email address assuming they have not provided you with one.