topic Re: TalkTalk SMTP server rejecting some connexions (but not all). in Email

TalkTalk SMTP server rejecting some connexions (but not all).

gmlack — Mon, 03 Nov 2025 17:33:20 GMT

I send my email via a local SMTP server (mine - Postfix).

This has worked well for several years.

But this morning, when I tried to send an email to 7 recipients, it failed and the log of connexions to TalkTalk shows:

2025-11-03T11:17:52.300609+00:00 benuc postfix/qmgr[1993]: 3699C5F2CB: from=<MyAccount@dsl.pipex.com>, size=3070, nrcpt=7 (queue active)
2025-11-03T11:17:57.392258+00:00 benuc postfix/smtpd[356593]: disconnect from mylaptop.homenet[192.168.1.10] ehlo=2 starttls=1 auth=1 mail=1 rcpt=7 data=1 quit=1 commands=14
2025-11-03T11:17:59.968276+00:00 benuc postfix/smtp[356597]: 3699C5F2CB: to=<Rcpt1@btinternet.com>, relay=smtp.talktalk.net[153.92.174.230]:587, delay=7.7, delays=0.09/0.02/0.26/7.3, dsn
=4.7.1, status=SOFTBOUNCE (host smtp.talktalk.net[153.92.174.230] said: 550 5.7.1 Reject for policy reason (in reply to end of DATA command))
2025-11-03T11:17:59.970646+00:00 benuc postfix/smtp[356597]: 3699C5F2CB: to=<Rcpt2@btinternet.com>, relay=smtp.talktalk.net[153.92.174.230]:587, delay=7.7, delays=0.09/0.02/0.26/7.3, dsn
=4.7.1, status=SOFTBOUNCE (host smtp.talktalk.net[153.92.174.230] said: 550 5.7.1 Reject for policy reason (in reply to end of DATA command))
2025-11-03T11:17:59.973066+00:00 benuc postfix/smtp[356597]: 3699C5F2CB: to=<Rcpt3@gmail.com>, relay=smtp.talktalk.net[153.92.174.230]:587, delay=7.7, delays=0.09/0.02/0.26/7.3, dsn=4.7.
1, status=SOFTBOUNCE (host smtp.talktalk.net[153.92.174.230] said: 550 5.7.1 Reject for policy reason (in reply to end of DATA command))
2025-11-03T11:17:59.976523+00:00 benuc postfix/smtp[356597]: 3699C5F2CB: to=<Rcpt4@gmail.com>, relay=smtp.talktalk.net[153.92.174.230]:587, delay=7.7, delays=0.09/0.02/0.26/7.3, dsn=4.7.
1, status=SOFTBOUNCE (host smtp.talktalk.net[153.92.174.230] said: 550 5.7.1 Reject for policy reason (in reply to end of DATA command))
2025-11-03T11:17:59.978996+00:00 benuc postfix/smtp[356597]: 3699C5F2CB: to=<Rcpt5@gmail.com>, relay=smtp.talktalk.net[153.92.174.230]:587, delay=7.7, delays=0.09/0.02/0.26/7.3, dsn=4.7.
1, status=SOFTBOUNCE (host smtp.talktalk.net[153.92.174.230] said: 550 5.7.1 Reject for policy reason (in reply to end of DATA command))
2025-11-03T11:17:59.981324+00:00 benuc postfix/smtp[356597]: 3699C5F2CB: to=<Rcpt6@hotmail.co.uk>, relay=smtp.talktalk.net[153.92.174.230]:587, delay=7.7, delays=0.09/0.02/0.26/7.3, dsn=
4.7.1, status=SOFTBOUNCE (host smtp.talktalk.net[153.92.174.230] said: 550 5.7.1 Reject for policy reason (in reply to end of DATA command))
2025-11-03T11:17:59.984062+00:00 benuc postfix/smtp[356597]: 3699C5F2CB: to=<Rcpt7@example.plus.com>, relay=smtp.talktalk.net[153.92.174.230]:587, delay=7.7, delays=0.09/0.02/0.26/7.3, d
sn=4.7.1, status=SOFTBOUNCE (host smtp.talktalk.net[153.92.174.230] said: 550 5.7.1 Reject for policy reason (in reply to end of DATA command))

It continues to give this response every time the Postfix server tries resending.

It appears that I can send emails to 1 addressee, e.g.:

2025-11-03T16:45:00.112865+00:00 benuc postfix/qmgr[1993]: 1401C5F419: from=<MyAccount@dsl.pipex.com>, size=2041, nrcpt=1 (queue active)
2025-11-03T16:45:01.591676+00:00 benuc postfix/smtp[371777]: 1401C5F419: to=<Rcpt1@icloud.com>, relay=smtp.talktalk.net[153.92.174.230]:587, delay=1.5, delays=0.05/0.01/0.25/1.2, dsn=2.0
.0, status=sent (250 2.0.0 Ok: queued as 64308A40142)
2025-11-03T16:45:01.592070+00:00 benuc postfix/qmgr[1993]: 1401C5F419: removed

so there's nothing wrong with authentication (and, indeed, I'm receiving incoming mail OK).

So, what has changed on the TalkTalk SMTP server (nothing changed at my end).?

Re: TalkTalk SMTP server rejecting some connexions (but not all).

gmlack — Tue, 04 Nov 2025 00:35:47 GMT

More details, and it's getting stranger.

That email , which was sent to 7 addressees, has not been sent to any of them.

But if I send an email to 6 of those (same) addressees then TalkTalk accepts it for 5 of them immediately, rejects the 6th but accepts that 6th one on its second attempt a few minutes later.

I can also send an individual email to the 7th addressee with no problem.

Re: TalkTalk SMTP server rejecting some connexions (but not all).

Philile-TT — Tue, 04 Nov 2025 07:15:53 GMT

@gmlack are you using webmail?

Re: TalkTalk SMTP server rejecting some connexions (but not all).

gmlack — Tue, 04 Nov 2025 12:43:20 GMT

No. I'm talking to the SMTP server at smtp.talktalk.net.

I'm also seeing occasional SMTP auth failures:

5.7.8 Error: authentication failed: (reason unavailable)

the same account is OK immediately after.

Re: TalkTalk SMTP server rejecting some connexions (but not all).

gmlack — Tue, 04 Nov 2025 22:37:31 GMT

Can no-one shed any light in why the TalkTalk SMTP server is responding:

(host smtp.talktalk.net[153.92.174.230] said: 550 5.7.1  Reject for policy reason (in reply to end of DATA command))

It's nothing at my end. I've been sending a similar message to the same 7 recipients every week for a few years with no problem until now.

Re: TalkTalk SMTP server rejecting some connexions (but not all).

amahle-TT — Thu, 06 Nov 2025 07:14:45 GMT

Hi there, please confirm if you are still experiencing the issue so we can proceed thanks.

Re: TalkTalk SMTP server rejecting some connexions (but not all).

gmlack — Thu, 06 Nov 2025 09:57:27 GMT

Yes. It's still happening.

I'm also seeing frequent:

5.7.8 Error: authentication failed: (reason unavailable)

messages when connecting to the SMTP server. (It's a temporary state - the authentication succeeds later without me doing anything).

This also only started this week.

Re: TalkTalk SMTP server rejecting some connexions (but not all).

amahle-TT — Thu, 06 Nov 2025 10:08:10 GMT

Can you check your TalkTalk Internet access for me now and let me know if it works? You can do this by trying to reload the site or application you were experiencing problems with, or trying to search for something on the Internet.

Re: TalkTalk SMTP server rejecting some connexions (but not all).

gmlack — Thu, 06 Nov 2025 10:26:52 GMT

Not sure what you mean by "TalkTalk Internet access", as I wouldn’t be seeing this and replying to it if I didn't have "TalkTalk Internet access". Receiving email is OK.

I've just sent an email to 3 recipients. This reported:

5.7.8 Error: authentication failed: (reason unavailable)

for all 3 addresses, but them when I forced postfix to resend it a minute later all was OK.

The original message I sent to the 7 recipients is still stuck and fails on every resend attempt. Either for:

5.7.8 Error: authentication failed: (reason unavailable)

550 5.7.1  Reject for policy reason (in reply to end of DATA command)

All of this only started to happen at the start of this week.

Re: TalkTalk SMTP server rejecting some connexions (but not all).

amahle-TT — Thu, 06 Nov 2025 10:26:59 GMT

I am about to run checks, and I need you to confirm if you have a stable internet connection before we start.

Re: TalkTalk SMTP server rejecting some connexions (but not all).

gmlack — Thu, 06 Nov 2025 10:28:44 GMT

Yes, I do.

It's current state is:

Uptime 2d 17h 48m 22s.
Last reset after 1d 09h 24m 01s.

Actual speed:

Download: 77155000
Upload: 19999000

Attainable speed:

Download: 98151000
Upload: 22888000

External addr: 89.x.x.x

Re: TalkTalk SMTP server rejecting some connexions (but not all).

amahle-TT — Thu, 06 Nov 2025 10:30:49 GMT

Thank you, what device are you using when accessing your email?

Re: TalkTalk SMTP server rejecting some connexions (but not all).

gmlack — Thu, 06 Nov 2025 10:53:46 GMT

Accessing email is OK.

It's just sending that is the issue.

I route all of my outgoing email through a postfix server, which is what connects to TalkTalk.

Re: TalkTalk SMTP server rejecting some connexions (but not all).

amahle-TT — Thu, 06 Nov 2025 10:56:52 GMT

I do understand that, and I am running checks so we can find the solution. I need to know what device are you using when accessing your email?

Re: TalkTalk SMTP server rejecting some connexions (but not all).

gmlack — Thu, 06 Nov 2025 11:01:20 GMT

Not sure what you mean by "device".

The postfix server is running an on an Intel NUC system running postfix on Kubuntu.

It connects though my Asus router and a Draytek modem.

Re: TalkTalk SMTP server rejecting some connexions (but not all).

amahle-TT — Thu, 06 Nov 2025 11:03:54 GMT

it can either be a Personal Computer or a

Laptop

Smartphone

Tablets

Gaming consoles

Re: TalkTalk SMTP server rejecting some connexions (but not all).

gmlack — Thu, 06 Nov 2025 11:09:43 GMT

It's none of these.

It's a postfix server process.

My email client talks to my postfix server. That postfix server then talks to TalkTalk.

Re: TalkTalk SMTP server rejecting some connexions (but not all).

amahle-TT — Thu, 06 Nov 2025 11:18:03 GMT

I understand that it is postfix server process, however in order to log onto your email client you would need to be using a device, we need to know what device you use to access your email client?

Re: TalkTalk SMTP server rejecting some connexions (but not all).

gmlack — Thu, 06 Nov 2025 11:19:56 GMT

I use Thunderbird on a PC.

But it never contacts TalkTalk directly.

Re: TalkTalk SMTP server rejecting some connexions (but not all).

amahle-TT — Thu, 06 Nov 2025 12:23:08 GMT

Thank you, I need to know the operating system on your PC?

Is it

Windows or Mac OS ?