Failded deliveries

[#1]

An email that I sent got a delivery failure notice status 5.7.1.
Please! Can someone tell me what that means, and if  it is something I can get round, preferably with guidance?
I use Thunderbird.

[#2]

We need the full error message - the number can mean several things.
SMTP error 5.7.1 normally means relay not permitted but can also mean sender ID not permitted or Access denied
This means the email server you are connecting too will not allow you to send mail through it. Hence the need for the full error message which normally gives additional info as to why.

[#3]

That's odd as the email address was that of my district councillor xx@ yy.gov.uk, whence from message source it appears they are passed on to his personal address with another ISP.I'd not have thought, he wanted to hide himself .
Any further comments, ideas?

[#4]

Not without the full error message as I said... with any email addresses suitably masked (as you have done), although the bit after @ would be useful to identify if there is a mail server related with the issue.

[#5]

I got round it,having found that his forwarding address was in the headers.