topic Re: Bouncing emails in Email

Bouncing emails

Pancho4 — Wed, 17 Sep 2025 11:25:41 GMT

My main email address on a domain hosted at Plusnet/Force9 seems now to be blacklisted/regarded as spam. An email from this address fails to send (using outlook) and I get the error message "Task 'address@domain.co.uk - Sending' reported error (0x800CCC78): 'Cannot send the message. Verify the email address in your account properties. The server responded: 550 <address@domain.co.uk> sender domain rejected (blacklisted by local policy)'

How do I get out of this situation please? This email has been in use for 20+ years and nothing seems to have changed on my side. Is this just a random blacklisting or something else? Many thanks

Re: Bouncing emails

Townman — Wed, 17 Sep 2025 12:52:43 GMT

First step is for you to lookup the black list status of your domain - see Email Blacklist Check - IP Blacklist Check - See if your server is blacklisted

Re: Bouncing emails

Silverwhistle — Wed, 17 Sep 2025 14:21:03 GMT

This has been happening to me since last night also. I contacted Plusnet via Twitter, but have had no response yet.

Re: Bouncing emails

Pancho4 — Wed, 17 Sep 2025 14:23:22 GMT

Thanks very much - but its not on the blacklist list!!

Re: Bouncing emails

Townman — Wed, 17 Sep 2025 14:46:02 GMT

That error code covers a multitude of sins as described here - Email Send Error - Microsoft Q&A

Can you please run the email server connection diagnostics (link below) and report back.

Re: Bouncing emails

Pancho4 — Wed, 17 Sep 2025 15:42:55 GMT

Thanks for the guidance. I think i have been able to follow the instructions hopefully. Running terminal gave:-

PS C:\Users\john> curl.exe -v imaps://imap.force9.net -u XXXX@xxxx.co.uk
Enter host password for user 'XXXX@xxxx.co.uk':
* Host imap.force9.net:993 was resolved.
* IPv6: (none)
* IPv4: 91.204.208.196
* Trying 91.204.208.196:993...
* schannel: disabled automatic use of client certificate
* schannel: next InitializeSecurityContext failed: CRYPT_E_NO_REVOCATION_CHECK (0x80092012) - The revocation function was unable to check revocation for the certificate.
* closing connection #0
curl: (35) schannel: next InitializeSecurityContext failed: CRYPT_E_NO_REVOCATION_CHECK (0x80092012) - The revocation function was unable to check revocation for the certificate.
PS C:\Users\john> curl.exe -v pop3s://mail.force9.net -u XXXX@xxxx.co.uk

I have anonymized the output but am unable to understand what it means please? Thanks for your help

Re: Bouncing emails

Townman — Wed, 17 Sep 2025 16:46:34 GMT

Hi John,

This looks like a server side issue with the security certificates. Would I be correct that you are trying to authenticate using your hosted domain name email address?

Just need to rule out a suspicion / narrow the scope of the issue. Can you please try again using...

you@youraccount.force9.co.uk
youraccount
youraccount+mailboxname

Also run the original command removing the "s" in the "imaps://" prefix - that tests an unencrypted connection. If that is successfully, it points firmly to an obscure certificate issue.

Re: Bouncing emails

Silverwhistle — Wed, 17 Sep 2025 18:17:01 GMT

Mine seems to have recovered now.

Re: Bouncing emails

Pancho4 — Wed, 17 Sep 2025 19:07:26 GMT

I tried with the email address id and omitting the s from imaps:-

PS C:\Users\john> curl.exe -v imap://imap.force9.net -u xxxx@xxxx.co.uk
Enter host password for user 'xxxx@xxxx.co.uk':
* Host imap.force9.net:143 was resolved.
* IPv6: (none)
* IPv4: 91.204.208.196
* Trying 91.204.208.196:143...
* Connected to imap.force9.net (91.204.208.196) port 143
< * OK IMAP4 ready
> A001 CAPABILITY
< * CAPABILITY IMAP4 IMAP4rev1 UIDPLUS AUTH=PLAIN STARTTLS
< A001 OK completed
> A002 AUTHENTICATE PLAIN
< +
> AGpvaG5AY3JlZXIuY28udWsAQjBsbDBja3Mh
< A002 NO Login failed.
* closing connection #0
curl: (67) Login denied

I'll work my way through the other options you indicated. Thanks

Re: Bouncing emails

Townman — Wed, 17 Sep 2025 19:14:11 GMT

I will add this to the odd ball list!

Re: Bouncing emails

Pancho4 — Wed, 17 Sep 2025 19:18:43 GMT

I tried with the three other logon credential options you suggested and got a very similar response to each other and the very first one using just the email address.

Thanks for your help

Re: Bouncing emails

Townman — Wed, 17 Sep 2025 19:30:57 GMT

For clarity, can you logon to the account using webmail?

Can you send using webmail?

What platform are you on?

Are you on network or off network?

From what you have reported...

You cannot send (that implied that you were logged on the the mailbox)
The IMAP diagnostic with encryption fails due to server name mis match
The IMAP diagnostic without encryption fails for not clear reason

I fear we might have become confused along the way here; you initially reported an issue with SENDING and I asked you to run the diagnostic tests which verify connections to all three servers IMAP and POP3 (inbound) and SMTP (outbound). You reported the IMAP results where I became focussed on the certificate error which echoes an issue reported elsewhere.

The IMAP text without encryption is thou also failing - which is confusing!

Can you please try using webmail, if you cannot log on there, then consider ...

Reset email password

If you are not able to login to the email address using webmail, then it is likely that your email address has been identified as being compromised and has had its password changed. Where email address passwords have been changed to protect the integrity of the service, the Plusnet account password is left unchanged.

Which ISP are you with, Plusnet or one of the other / legacy vISPs?

Plusnet / Force9 / FreeOnline users can only change the password on the DEFAULT email address by changing the password on the user ACCOUNT through the user portal. You can change the password on a secondary mailbox using the Manage My Mail options in the user portal.

Brightview users (Madasafish / FreeNetName / GlobalNet / IC24 / ICScotland / Dialstart / Totalise) logging into webmail should use their full email address. Use the MAAF user portal to update the password on the default email address (change the account password) and use this MAAF guide to change the password on a secondary mailbox address. If you cannot recall the account password, you will need to contact support ... because the account password change process sends an email to the mailbox you cannot now access.

DO NOT USE THE SAME PASSWORD AGAIN for that would allow the continued exploitation of the account. The new password should be cryptic and not one used before.

Note that changing the account password will change the password used for logging on to the relevant user portal. If your email service is NOT a retained legacy service (one associated with a retired internet service account), then the password required by the router to connect to the internet will be changed too. If the router is a Hub Zero or a Hub One supplied by Plusnet it should update automatically. If not, you will need to log into the router, drop the connection, change the password yourself and reconnect.

On the assumption that the email address password has been compromised, I strongly recommend that wherever you have used that email address / password combination as access credentials to services such as Amazon, Netflix, eBay etc., that you also change the passwords on those service as well.

Re: Bouncing emails

Pancho4 — Thu, 18 Sep 2025 09:09:51 GMT

Hi, Thanks for your help.

To answer your questions;-

I have logged on to webmail OK for all my mailboxes and sent OK. Of course the password for the mailboxes are different from the login password to the mail server in Outlook.

I use Windows 11 and Outlook - on a private home network. I'm with Plusnet/Force9

The error message from Outlook has now changed as the mail.plus.net server is now asking for user name and password input - and then rejects the login. The password has not altered however.

Is the next step to reset the password on the mail server? Thanks for your patience and help!

Re: Bouncing emails

Townman — Thu, 18 Sep 2025 10:23:33 GMT

The next step is to rerun the diagnostic across the mailboxes.

The default address needs to account password.

The secondary addresses have their own.

An alarm bell has rung - proper (paid for) Outlook or the free excuse for Outlook? If the latter you might well be better off switch to a decent email client such as eM Client. Free Outlook can be a pig to configure.

You do though first need to have confidence that there are no other issues - a successful diagnostic test will do that.

Re: Bouncing emails

Pancho4 — Thu, 18 Sep 2025 11:20:45 GMT

Hi,

I ran the diagnostic test again:-

PS C:\Users\john> curl.exe -v imaps://imap.force9.net -u xxxx@xxxxx@f9.co.uk

Enter host password for user xxxx@xxxxx@f9.co.uk:

* Host imap.force9.net:993 was resolved.

* IPv6: (none)

* IPv4: 91.204.208.196

* Trying 91.204.208.196:993...

* schannel: disabled automatic use of client certificate

* schannel: next InitializeSecurityContext failed: CRYPT_E_NO_REVOCATION_CHECK (0x80092012) - The revocation function was unable to check revocation for the certificate.

* closing connection #0

curl: (35) schannel: next InitializeSecurityContext failed: CRYPT_E_NO_REVOCATION_CHECK (0x80092012) - The revocation function was unable to check revocation for the certificate.

This seems to suggest that the account password I am using is correct?

The outlook version I am using is a genuine paid for microsoft version.

However - we also use two ipads for mail, my wife and I, and I now realise that emails with different mailboxes off the same host domain off separate ipads, now do not appear to be sending. Error message = "Cannot get mail - mail server mail.force9.net is not responding. Verify you have entered the correct account info in mail settings". Network error (POSIX 96)

This would suggest that the problem is not a software/device dependant issue at our end.?

Sorry to be a nuisance and thanks for your patience

Re: Bouncing emails

Townman — Thu, 18 Sep 2025 15:45:02 GMT

Hi John,

Not a nuisance at all, just tricky issues this week.

Today there were issues with the network which has impacted some user's access to email, but not everyone's as has been the case recently with the email service itself.

The response does NOT suggest one way or another the validity of the password, in fact I an suspicious of the userID in the text you have redacted...

curl.exe -v imaps://imap.force9.net -u xxxx@xxxxx@f9.co.uk

Unless there is a typo in there, the email address is mal-formed. It should be...

curl.exe -v imaps://imap.force9.net -u xxxx@xxxxx.f9.co.uk

That said using really bad credentials of the form above does not give rise to your error - I just get failed login...

< A002 NO Login failed. * closing connection #0 curl: (67) Login denied

What platform are you on and are you using PlusNet as your ISP?

Apple devices - please try again.

To to be sure that there were no transient issues, can you please confirm if the email application can login to the IMAP server and then try to send again ... which is where we started!!

@plusnettony

I am stumped here now ...

This started off as a SMTP black listed IP address
It has morphed into a IMAP diagnostic failure on certificate revocation
IMAP diagnostic without security (to eliminate the certificate factor) cannot login

Re: Bouncing emails

Pancho4 — Thu, 18 Sep 2025 16:34:19 GMT

Sorry - yes there is a typo in the redaction of the user ID

I am on windows 11 and Plusnet/Force9 is my ISP

When I try to send from my main email address now on an ipad to another valid email address, I get the message cannot send mail and that both email addresses are not valid email addresses and are rejected by the server (and message placed in the outbox). I don't get a logon error, so presumably I can logon ok to the server?

puzzled!

Re: Bouncing emails

Pancho4 — Fri, 19 Sep 2025 09:39:52 GMT

I’m getting frustrated with this email problem. I thought it might help to summarise the present situation.

It all relates to emails from addresses off my main domain hosted on Plusnet/Force9
It is occurring on my different devices – Home PC running Windows11 + Microsoft outlook – and two ipads using the apple mail application.
But the problem manifests itself differently in the two different environments and has seemed to evolve.
Windows11 PC – when I do a send/receive command in outlook I get the prompt – enter user name and password for the following server “mail.plus.net” + User name (visible) + Password (hidden)
1. I enter the correct password and press “OK”
2. The send/receive fails “ERR login fails” – verify user name and password in Account settings
3. So, no mail is currently being received or sent from this email address
4. I know that the user name and password being used is correct because I can go into webmail successfully and use all the functions
5. When I try to verify the password in account settings the process fails “something went wrong …..”
Ipads – Messages to email addresses off my domain are being received, but no messages can be sent.
1. If I try and send with a home main domain email address to someone else, or if I send from a @gmail.com or @me.com address then I get the same message each time :- “xxxx@xxxx.com and xxxx@xxx2.com are not valid email addresses and have been rejected by the server”

Where do I go from here please?

Re: Bouncing emails

Townman — Fri, 19 Sep 2025 09:45:15 GMT

relates to emails from addresses off my main domain hosted on Plusnet/Force9

enter user name and password for the following server “mail.plus.net”

If this is a FORCE9 mail service then the server should be mail.force9.net (for POP3)

If this is an IMAP configuration then the server should be imap.force9.net

Re: Bouncing emails

Pancho4 — Fri, 19 Sep 2025 13:12:19 GMT

Hi Townman,

I'm not certain that changing the POP3 server to Force9.net is the issue. Firstly, when I try to amend the server details in the Accounts settings section, and also using the manual repair option it doesn't allow an update with the message "something went wrong and outlook couldn't save your account settings",

Secondly this problem surely cannot be due to a fault in the Outlook settings which were working fine until a couple of days ago and nothing systemwise has changed here - and why also are there problems now with this email address on the ipads with apple mail which didn't occur before? This suggest the problem lies at the ISP end AND

now I am even more confused now as I have just had the following email from support@force9.co.uk, namely:-

"Username: xxxxxx

You are receiving this message as your mailbox has not been accessed since: 2025-04-25 16:37:24

We have therefore archived the contents of the mailbox, please note that new mails will continue to be received.

To stop this from happening going forward you need to access it and collect E-Mail at least once within a 90 day period.

If you would like your email restoring then please contact our support team by raising a ticket using the Help Assistant on our website:

https://portal.plus.net/

We will only keep archived email for a limited period of time, after which it will be permanently deleted.

Kind regards,

Plusnet customer support

https://portal.plus.net/="

I have used this mailbox daily for the last 25 years or so - so that message doesn't make sense. Really grateful for any clarity on how to rectify this situation.

cheers and thanks