Can decrypt only one email of many from the same sender

[Baub L]

I am working on installing email and rolling it out for my company so we can use PKI with our emails. The setup of enigmail into Thunderbird went fine and everyone is able to generate their certs, we upload the public cert to the server for others to download.

In testing I received 3 emails, all encrypted, from the same sender within just a few minutes. I noticed the first email (which I was able to decrypt) had the following:

Note: The message is encrypted for the following User ID's / Keys:
0xBDDXXXXXXXC3BF22 (sam sam@mysite.com),
0x529XXXXXXXX2D0D6 (bob bob@mysite.com)

The second and thrid email had this (I am not able to decrypt these emails)

Note: The message is encrypted for the following User ID's / Keys:
0x529XXXXXXXX2D0D6 (bob bob@mysite.com)

My email is the sam email. Can someone explain to me what the user is doing different to encrypt the emails? I am not able to see what they are doing to have this happen.

[Rob]

My email is the sam email. Can someone explain to me what the user is
doing different to encrypt the emails? I am not able to see what they
are doing to have this happen.

They're giving an additional recipient, either on the command-line (via
the --recipient option) or in gpg.conf (via the recipient option). It's
nothing to be surprised about -- it's perfectly normal to encrypt for
multiple recipients.