Mail being sent by CFMAIL blocked by some ISPs

[Guest]

I have written an app for a client which sends emails as part of confirmation. We have noticed that some domains will block the email ie btinternet.com email addresses will block the emails. However, if the client emails from their own email address the customer will receive this email. What could be blocking this email?
We are using CF9

Here is my email code:
<cfmail to="#customer_email#" from="#from_email#" bcc="#blankemail#" subject="#email_subject#" type="html">
<cfmailpart type="text/plain">
<cfoutput>#plain_email_text#</cfoutput>
</cfmailpart>
<cfmailpart type="text/html">
<cfoutput>#html_email_text#</cfoutput>
</cfmailpart>
</cfmail>

[WolfShade]

It's most likely due to the sending domain being blacklisted by some spamlist authority.  If this is the case, it's usually returned with a message explaining why.  Check to see if there are any return messages from the domains that are blocking the email.

^_^

[Kaif_Akbar]

Have you checked mail log file from CF 9 server? Is there any relevant logging for it?

Kindly also check below bug detail and confirm, either you are getting similar issue too:-

https://bugbase.adobe.com/index.cfm?event=bug&id=3373350

Regards,

Kaif Akbar