SMTP Authentication schizophrenia

[tjcmorgan]

Hi there-

I have two btconnect accounts configured in Mac Entourage that work properly nearly all the time (sending and receiving). Occasionally, one or both of them can't send mail (due to server "authentication" errors) - sometime refusing passwords. Nothing has been changed on the client.

To "fix" the problem, I have either had to enable SMTP authentication or disable it (i.e. the reverse of what worked before).

So, I know how to workaround the issue, but why is it happening in the first place. Is BT changing the SMTP policy?

--

tm

[alastair]

its the way that BTs server DONT work.

it seems to happen alot.

i found rebooting the router fixes it alot of the time. something to do with the server not liking the ip address i suspect

[adrianc]

"...something to do with the server not liking the ip address i suspect"

Close, but not quite. The issue is that mail.btconnect.com is a CNAME for a farm of servers. Most of them advertise that they require SMTP authentication, but some do not. When the client attempts to send mail, if mail.btconnect.com is resolved to one of the correctly configured servers, authentication will work a treat. However, if it resolves to one of the other ones it will not - but only with some clients (Mac Mail and Outlook 2007 being the most common).

Of course, if your PC/Mac/router is caching DNS answers (as it should), you will continue to hit the same server until the expiration of the DNS result (a quick check gives me a 600 second TTL). Rebooting the router will 'fix' the problem as (a) it will eat up a significant portion of the 600 seconds; and (b) it will likely result in a new lookup that might hit a different server.

[alastair]

why do BT have differently configured servers? surely if they knew this was what caused so many people to complain about BTs email service then they would configure them to be the same?

[adrianc]

That is a question I've been searching for an answer to for a long time. The closest I have gotten to a sensible answer is that is is the result of a migration project that never got completed.

To be fair though, it only causes a problem with clients that treat the AUTH response as gospel, most will try it anyway and will be able to send.

[alastair]

hallelujah!

[Kirok]

I wondered this myself ages ago anyway short answer - they turned on authentication for some servers because they wanted to see how many customers already had SMTP authentication turned on... and of course its not configured correctly or set to fallback gracefully.

The server pool list is online, I tested them ages ago to see which server supported what but I can't find the text file.

[alastair]

welcome back kirok.

apparently... and this is because i was assisting a family friend that i know this...

BTinternet now only allows email to be sent when authentication is on and their site www.btyahoo.com/smtp (i think its that one) said that in order to combat spam all ISPs will be making everyone turn authentication on. which is fair enough.

wonder when BTconnect are going to start that. and if so i imagine they will then make all their servers require authentication meaning that the servers will be configured the same.

[Kirok]

Cheers, I occasionally pop in and out, or lurk depending on what else I'm doing or how bored I am and if someone else has answered the question.

I know BT Internet run things a bit differently I've even seen them blacklist each other on occasion, further to the SMTP survey explanation my guess is they were seeing if they could move wholey over to SMTP auth without customers complaining, probably because they were being killed by spam.

[alastair]

but.... they CAUSED complaints with non comformity between servers.... how can they judge the effects properly if it caused other issues. o well..