Sent a email to some friends and some bounced

[#1]

I sent a humour email to friends that contained an inserted image. All four are Plusnetters, but two have bounced back with similar warnings

A message that you sent to the following recipient could not be delivered due to a permanent error. ** The remote server 212.159.9.***responded with: ** adam@aaaal.plus.com 550:#5.1.8 Domain of sender address <***@bbbbb.plus.com> does not exist This message was created automatically by mail delivery software on the server avasout04.

, Two of the four have discrete user names and one of theirs did get through it seems, and two are users of a organisations user name, Likewise one of the two got through.
All were as bcc, and are in my address book and sued many times
Explanation please

[#2]

Oh dear, avasout04 strikes again.
The message actually relates to your (sender) domain appearing not to exist when that relay server checked. The domain probably doesn't exist in the sense of having an A (website) record, but it will have an MX (email) record, and that should be an acceptable substitute, and was for two of the addressees.
If you try sending the message again (either to all 4 or just the two failures as you wish) it will probably be fine.
David
Edit: a typical raw error message from the relay server is illustrated in the dialogue below. Note that the message appears before any addressee has been mentioned

c:\> telnet relay.plus.net 25
Trying 212.159.9.107...
Connected to relay.plus.net.
Escape character is '^]'.
220 avasout06 smtp relay.plus.net
ehlo hello
250-avasout06 hello [xx.xx.xx.xx], pleased to meet you
250-HELP
250-AUTH LOGIN PLAIN
250-SIZE 104857600
250-PIPELINING
250-8BITMIME
250 OK
mail from:<tommy@idontexist.plus.com>
550 <tommy@idontexist.plus.com> sender rejected - invalid domain (no MX or A record) <---
quit
221 avasout06 smtp closing connection