Certain Mail services are rate limiting emails being sent to them meaning they only accept a few emails an hour from our mail servers. We're in discussion with them to get a white-list in place to bypass this, but there's no ETA as to when this might occur, as the block is in place at their end.
Mail services currently affected are:
AOL
BT
Hotmail/Outlook
Our current recommendations are to change the Outgoing Mailserver to one of the below, and to add an SPF record. Please open a
ticket for more assistance on this matter.
mail31.extendcp.co.uk,
mail32.extendcp.co.uk
mail33.extendcp.co.uk,
mail34.extendcp.co.uk,
mail35.extendcp.co.uk