Email does not reach intended recipients 550 spam , or phishing or malware

[Horto01]

I am getting email returned with message 550 spam, or  phishing or malware  with  codes (6 - 1 - 3 - 2) ID (613A91241C049319)

Can you help please 

[NeilO]

Hi, @Horto01 Welcome to the community and thanks for posting, I'm sorry to see you're having problems sending email. Does this happen to all emails or one in particular and can you send it if you login to www.bt.com/email 

The error 550 means the spam filters have picked up something suspicious within the email or your IP address and have blocked it to try to prevent the BT email system from being abused but sometimes it gets this wrong.

Thanks

Neil

[Horto01]

It seems to apply to one particular email which has been back and forth between ourselves and a particular company as a sort of conversation.

I have tried new emails to the three recipients involved and they appear to go through successfully