This topic

SMTP stopped working after changing Broadband speed

JohnMcDonald707 — Fri, 28 Mar 2025 16:16:53 GMT

Has anyone had problems with SMTP mail client after upgrading their broadband to 900Mb fiber broadband.

That is can't send email after changing to a higher speed (bandwidth) broadband

John

SMTP

JohnMcDonald707 — Fri, 28 Mar 2025 17:24:15 GMT

My SMTP email stopped working when I upgraded to 900Mb broadband. Has anyone else experience this problem ?

John

Re: SMTP stopped working after changing Broadband speed

JohnMcDonald707 — Fri, 28 Mar 2025 17:30:20 GMT

Just joined a test reply to poster

Re: SMTP stopped working after changing Broadband speed

Peter_W — Sat, 29 Mar 2025 09:15:18 GMT

Hi @JohnMcDonald707.

Welcome to the BT Community!

I'm not aware of any similar reports around this; which client is it you're using and is this on a PC or mobile / tablet.

Have you tried seeing if you can send successfully through BT Webmail too?
Peter

Re: SMTP stopped working after changing Broadband speed

JohnMcDonald707 — Sat, 29 Mar 2025 10:32:10 GMT

Hi Peter,

Much discussion with BT and a ticket raised.

To cut a very long story short BT will not check the SMTP server/comms interface whilst I send some test emails.

Before retiring spent a good 40 years on networks connecting computer system/data transmission and suspect the SMTP Sever / comms interface can't authenticate at the higher data rate and drops the connection. When I go back to a 250Mb broadband all works fine again.

We have the classic multi-vendor situation here Fibre network is City Fibre , the ISP is Toob and the mail service is BT Mail. I also have a Virgin Media SMTP account and that works fine over the 900Mb broadband

Thanks for taking a interest

Re: SMTP stopped working after changing Broadband speed

Peter_W — Sat, 29 Mar 2025 10:41:45 GMT

Thanks for explaining there @JohnMcDonald707.

When was it you raised this ticket, and were you advised if you would receive any further updates?

I can definitely highlight this with our email team to see if we've noticed anything similar, but I just want to be sure I'm not retreading old ground 😊

Peter

Re: SMTP stopped working after changing Broadband speed

JohnMcDonald707 — Sat, 29 Mar 2025 10:46:27 GMT

Sorry Peter,

Just to confirm you questions, no problems with web mail web access( http).

Conducted tests from tablets running Samsung Mail and Laptop running Outlook 2010.

Carried out Trace Route to check there is a path to server over the 900Mb broadband. BT has disabled Ping on Server.

Thanks and kind regards,

John

Re: SMTP stopped working after changing Broadband speed

iniltous — Sat, 29 Mar 2025 10:53:53 GMT

So it’s City Fibre that provide your broadband not BT , and although it’s reasonable to ask about your BT Email access , you don’t make it clear that BT are not your broadband provider.

Do you pay for premium email access to continue to use your BT email address with an email client , or are you on the basic webmail access ?

TBH , it’s a little misleading to say you have ‘upgraded’ to 900Mb , that implies you have maintained BT as your provider albeit with a ‘faster’ service, it’s not an upgrade in the accepted sense, you have joined City Fibre , not upgraded .

Re: SMTP stopped working after changing Broadband speed

JohnMcDonald707 — Sat, 29 Mar 2025 11:07:33 GMT

Ticket is VOL013-XXXXXXXXXXXX contact Heather Received a dead lock letter.

The issue is BT are not able/prepared to do an end to end test which is the only way to solve this comms/server interface problem.

I will be the first to say this is an odd fault.

Thanks again,

John

Re: SMTP stopped working after changing Broadband speed

JohnMcDonald707 — Sat, 29 Mar 2025 11:21:34 GMT

I have premium email access £7.50 per month.

I did not mention who the Broadband was provided by initially as it should not be be relevant to the problem

I upgraded my broadband ( increase bandwidth/speed) by moving from Virgin Media 250Mb coax to 900Mb optical fibre installed by City fiber.

I would love to have BT Fibre but they do not supply to my Estate. So I am stuck with a muilti-vendor set up for my email,

But if the correct technical description is required to help with solving problem it is what Ofcom calls a One Touch Switch.

Re: SMTP stopped working after changing Broadband speed

JohnMcDonald707 — Sat, 29 Mar 2025 11:36:53 GMT

It would be good to know if anybody in the Forum has a 900Mb BT Broadband service and uses STMP/POP/IMAP email.

John

Re: SMTP stopped working after changing Broadband speed

licquorice — Sat, 29 Mar 2025 11:43:04 GMT

I guess you didn't learn about flow control in your 40 years of networking.

Re: SMTP stopped working after changing Broadband speed

JohnMcDonald707 — Sat, 29 Mar 2025 12:03:39 GMT

I have no idea why you should make this comment about me . What is the basis for it? I tend to give my experience here to deter people thinking what I am saying has no value. On the face of it, flow control would seem to be the problem in this case with the SMTP server/front end router. Is this what you are trying to say?

SMTP stopped working after changing Broadband speed

JohnMcDonald707 — Wed, 02 Apr 2025 08:21:26 GMT

Hi Peter,

Did you highlight the problem to email team?

Thanks,

John

Re: SMTP stopped working after changing Broadband speed

Peter_W — Wed, 02 Apr 2025 11:10:35 GMT

Hey again @JohnMcDonald707.

I last received an update this morning advising they'll raise it with the relevant team.

If I get any further updates or need any specific details from yourself, I'll let you know!

Peter

Re: SMTP stopped working after changing Broadband speed

JohnMcDonald707 — Wed, 02 Apr 2025 13:29:59 GMT

Thanks Peter

Re: SMTP stopped working after changing Broadband speed

David_W102 — Thu, 16 Apr 2026 16:56:26 GMT

Yes - I'm having real problems here with my new 900mbps service and sending (SMTP) bt emails - Did anybody see a way out of this.

Re: SMTP stopped working after changing Broadband speed

Peter_W — Fri, 17 Apr 2026 09:47:11 GMT

Good morning @David_W102.

Just to double check, which client are you normally using to send, and do you get the same issues if you try BT Webmail?

Also is your 900 Mbps service on BT, EE, Plusnet, or another ISP?

Peter

Re: SMTP stopped working after changing Broadband speed

David_W102 — Fri, 17 Apr 2026 10:42:00 GMT

Hi Peter...

So in answer to your questions:

Which client are you normally using to send: I normally use Thunderbird, But have also tried Outlook 2024. Both appear to be either not working or as I have noticed today , working but very slow to process a sent message.

Do you get the same issues if you try BT Webmail? : No - If I use a web based app I don't see a problem, messages get sent fine.

Also is your 900 Mbps service on BT, EE, Plusnet, or another ISP? I was using TalkTalk (FTTC) until recently. With them emails were sending fine. I have noticed the issue now I have moved to Full fibre with Toob.com. But this could just be a coincidence as overall I have found the Toob service to be working well re general web based working.

Thanks

David

Re: SMTP stopped working after changing Broadband speed

licquorice — Fri, 17 Apr 2026 13:46:01 GMT

I suspect Toob IP address pool is the problem here, there are other posts from Toob customers having mail problems.