"Tom Wall" <TomW***@discussions.microsoft.com> wrote in message
news:82DFC9E4-7453-4033-9A77-51AF956D7C3F@microsoft.com...
> One of my users works remotely. He uses Outlook and POP/SMTP to send and
> receive mail.  He starting receiving this error intermittently when trying
> to
> send e-mails with file attachments.  His local ISP is Comcast or
> BellSouth.
> He may be set to authenticate with them when sending outgoing mail, which
> Comcast or BellSouth then forwards to our mail server. To make it even
> more
> fun, we have a hosted SPAM/security solution which filters and forwards
> our
> mail.
> Your message did not reach some or all of the intended recipients.
>      Subject:            RE: e mail to Jackie
>      Sent:                 2/13/2009 10:23 AM
> The following recipient(s) could not be reached:
>      'Tom Wall' on 2/13/2009 10:23 AM
>            450 [TEMPFAIL] ourdomainname.com requires valid sender domain
>
> I would appreciate any help you can provide.  Thanks.

"Ed Crowley [MVP]" <curspice@nospam.net> wrote in message
news:%235r1la9jJHA.4976@TK2MSFTNGP06.phx.gbl...
> It looks to me like he's sending his SMTP through BellSouth's SMTP server
> using his reply address on your server.  This is necessitated by
> BellSouth's restrictions on their customers connecting via SMTP to foreign
> servers in order to prevent their customers from generating SPAM, which
> can happen when they're infected by viruses and worms.  Very reasonably,
> BellSouth's doesn't have an SRV record for his SMTP address that matches
> your e-mail domain, so recipients who check that sort of thing as an
> antispam measure are bounding his mail.
>
> The best answer is for him to use RPC over HTTPS to connect to your
> Exchange server instead of using POP and SMTP.
> --
> Ed Crowley MVP
> "There are seldom good technological solutions to behavioral problems."
> .
>
> "Tom Wall" <TomW***@discussions.microsoft.com> wrote in message
> news:82DFC9E4-7453-4033-9A77-51AF956D7C3F@microsoft.com...
>> One of my users works remotely. He uses Outlook and POP/SMTP to send and
>> receive mail.  He starting receiving this error intermittently when
>> trying to
>> send e-mails with file attachments.  His local ISP is Comcast or
>> BellSouth.
>> He may be set to authenticate with them when sending outgoing mail, which
>> Comcast or BellSouth then forwards to our mail server. To make it even
>> more
>> fun, we have a hosted SPAM/security solution which filters and forwards
>> our
>> mail.
>> Your message did not reach some or all of the intended recipients.
>>      Subject:            RE: e mail to Jackie
>>      Sent:                 2/13/2009 10:23 AM
>> The following recipient(s) could not be reached:
>>      'Tom Wall' on 2/13/2009 10:23 AM
>>            450 [TEMPFAIL] ourdomainname.com requires valid sender domain
>>
>> I would appreciate any help you can provide.  Thanks.
>