are ip adresses unique---clarification...

I'm using a third party application to track my emails.  

I sent an email to person A at IP address AAAAAAAAA....the software
reports that she opened and read etc this email on IP addresss
AAAAAAAA. Serveral minutes later, the report shows the same email
being opened and read from Person B at IP address BBBBBBBBBBBB.

Seperate emails to Person B confirm his IP addresss of BBBBBBBBBB...is
there any way at all that person A did not forward my email to person
B?

Perhaps person A and person B are the same person, with two computers
at his/her desk, connected to separate networks, and he/she wanted to
read your email on both of them?

Owain

IP addresses must be unique to the network on which they are located.

So if an IP address of 123.123.321.321 exists on the internet, a
second computer may not use the same IP address on the Internet.
Similarly, my Mac currently uses IP address 150.150.10.154 on our
company network, so no other computer on this network can use the same
IP. However, another computer on a different network can certainly use
the same IP address as me because the two networks are independent of
each other.

Does that help?

Your question can not be answered because there is no hard connection
between an IP address and an email address. That answer depends on
what exactly you are tracking.

I recommend that you add information about what tracking software you
are using, and perhaps even post the tracking report. You can change
the email address to protect the innocent.

The senario you describe is perfectly plausible. For example, I
usually screen my email via a web browser for spam before I run my
email client. When I am at work, I logon to my ISP and look in my
email account logon box. I am accessing the email from my work PC,
hence the IP address I happen to have at work at the time.

That night when I get home I fire up my home PC and run my email
client. The client fetches the emails from the server and allows me to
respond to them. This time it is from the IP address I am using at
home at that time.

Second, most people using dial up internet accounts, and even people
using broadband at home and at work are not hard assinged an IP
address. They lease an IP address from a pool of available addresses
for as long as they are online. So I could dial up once and check my
email, and one IP address is reported. Then 30 minutes later logon
again and check again, with a new IP address. It's a crap shoot. You
don't know what address you will get. Because it doesn't matter.

So, please tell us what tracking software, and the report, and you
will get an sensible answer.