In a nutshell, it just means proving you are who you say you are and not a spammer.
This is what the bounce back looks like. I've anonymised the email addresses. To the recipient it looks like my email address has been permanently erase by BT. Come on BT please sort this out.
This message was created automatically by mail delivery software.
A message that you sent could not be delivered to one or more of
its recipients. This is a permanent error. The following address(es)
SMTP error from remote server for GREETING command, host: mx.bt.lon5.cpcloud.co.uk (220.127.116.11) reason: 554 rgin06.bt.int.cpcloud.co.uk Service not available - access denied
Yesterday I spent a bit of time looking at the SPF record on my primary domain. As I don't really understand it and don't want to make matters worse I invoked 1&1's call back system.
Well that takes you back to level 1. I told them that I expected them to sort out the SPF record as my ISP and went through the issue yet again. It has now been re-escalated and I await a further reply email.
I have been with 1&1 for many eyars but this issue with BT is driving me mad.
Just add the text string I posted, if it doesn't work just delete it again nothing to be lost in trying it.
I think I've solved the problem by dumping BT as my ISP and signing up with SSE. Saving £30 a month (BT = £52, SSE = £22) and because I already have SSE as my electricity supplier the price is frozen for 3 years