Outgoing password not recognised

[#1]

I have been using this machine and Outlook for years without changing anything. Suddenly the "Enter your user name and password" box has started popping up. usually this goes away again after a few hours, but has been a "feature" at least since Sunday.

Mails are coming in, I just can't send. 

I have a different mailbox connected to Thunderbird, which also can't log in.

I haven't changed any passwords or any other settings.

Any ideas?

[#2]

I've had this as well from this morning onwards, and it looks like a few others have too.

[#3]

Moderator's note:
Thread moved from Broadband to Email on assumption that the issue is referring to Email, not the Broadband account.

[#4]

Run the email server connection diagnostics - link below.

[#5]

I think I did that right. I tried with my username, and separately, email address. (me@username.f9.co.uk) I got "login denied" and "Invalid login or password", despite the facts that:

that password worked when I logged into the portal immediately before trying the test.

That password works for webmail

that password works to receive mail.

I have just gone into webmail and sent myself a message which arrived in outlook.

As i mentioned, I have had this problem before, but it usually disappears after a few hours, but not this time.

[#6]

Login denied on which server?

Are you on the Plusnet network?

Is this a default or secondary mailbox?  If secondary, try username+me as the user name.

Webmail is within the Plusnet network and is therefore a simpler login 'journey'.

[#7]

Using my username I got:  (Quietboy3 is this machine, of course)

Enter host password for user '--ssl-reqd':
* Host relay.force9.net:587 was resolved.
* IPv6: (none)
* IPv4: 91.204.208.196
* Trying 91.204.208.196:587...
* Connected to relay.force9.net (91.204.208.196) port 587
< 220 mail.enmail.co ESMTP ready
> EHLO Quietboy3
< 250-mail.enmail.co
< 250-AUTH PLAIN LOGIN
< 250 STARTTLS
> AUTH PLAIN
< 334
> <redacted>
< 535 5.7.0 Invalid login or password
* closing connection #0
curl: (67) Login denied

For my email address (I have reacted my username) I tried twice, and it seems to have tried IMAP the first time and POP the second, I use POP for Outlook (IMAP for tablets, phone etc) 

PS C:\Users\Leigh> curl.exe -v imaps://imap.force9.net -u leigh@XXXX.f9.co.uk
>> curl.exe -v pop3s://mail.force9.net -u leigh@XXXX.f9.co.uk
>> curl.exe -v smtp://relay.force9.net:587 -u leigh@XXXX.f9.co.uk --ssl-reqd
Enter host password for user 'leigh@XXXX.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
* Connected to imap.force9.net (91.204.208.196) port 993
< * OK IMAP4 ready
> A001 CAPABILITY
< * CAPABILITY IMAP4 IMAP4rev1 UIDPLUS AUTH=PLAIN
< A001 OK completed
> A002 AUTHENTICATE PLAIN
< +
> <redacted>
< A002 NO Login failed.
* closing connection #0
curl: (67) Login denied

Enter host password for user 'leigh@XXXX.f9.co.uk':
* Host mail.force9.net:995 was resolved.
* IPv6: (none)
* IPv4: 91.204.208.196
* Trying 91.204.208.196:995...
* schannel: disabled automatic use of client certificate
* Connected to mail.force9.net (91.204.208.196) port 995
< +OK POP3 ready <923957949.1752848973@mail.enmail.co>
> CAPA
< +OK Capability list follows
< TOP
< USER
< UIDL
< SASL PLAIN LOGIN
< .
> AUTH PLAIN
< +
> <redacted>
< -ERR Login failed.
* closing connection #0
curl: (67) Login denied
Enter host password for user 'leigh@XXXX.f9.co.uk':

(I hope my password isn't hidden there somewhere...)

Moderator's note:
Personal information removed from a public forum (to an area that staff can see).

Thanks for your help.

[#8]

The problem seems to have gone away (touch wood). It usually does so after a few hours, this time it has taken a week. Still no idea what causes it.

[#9]

The items in my outbox still won't go, though.

[#10]

This space is being worked on.

For the time being, OFF NETWORK SMTP authentication must use account+mailbox

However, if that means account+mail.box then authentication will not work at all.  I will chase the status on this.

EDIT: Update - for FORCE9 users, it rather looks as thought the use of the EMAIL ADDRESS for logging on to mail servers (for both the default and secondary mailboxes is fixed on and off network...

... but now username+mailbox does not - I will escalate!!

[#11]

Sorry, I don't understand what you are saying, but the problem of requesting the password (as if the saved one is incorrect) is back,

This is my main email and doesn't use a mailbox. It's just user@ f9.co.uk, not user+mailbox@....

Thanks