I have a SBS2008 server running Exchange 2007 over a BT Broadband connection. Email works fine with the exception that delivery of some btconnect address are delayed and may not arrive at all. Sometimes they are delivered but after an extended period.
I have worked through Alan Hardisty's document (https://www.experts-exchange.com/Software/Server_Software/Email_Servers/A_2427-Problems-sending-mail-to-one-or-more-external-domains.html
) which has always served me well but on this occasion, although everything seems to check out OK, I still have the problem. No doubt it's something I've missed but it escapes me as to what it is.