problems sending an email

i am with o2 for my broadband and use bluebottle as my email my outgoing server has to be relay.o2broadband.co.uk or i cant send emails which has never been an issue but if i email the missus at her work i get the following error email

- These recipients of your message have been processed by the mail server:
amy@./(deleted this part of email for obvious reasons).co.uk; Failed; 5.1.1 (bad destination mailbox address)

Remote MTA rhea.easily.co.uk: SMTP diagnostic: 550 "Mail from bluebottle.com is denied from host 87.194.255.143 SPF"


can anyone tell me what the hell this means i have no problems emailing anyone else.