Groups of Exchange emails truncate at 20 characters- why?

I am sending an email to a large group containing around 800 accounts.  There are a few accounts that have longer account names (more than 20 characters).  These emails are truncated at 20 characters and will not send.  It is my understanding that email addresses can be longer that 20 character, so I'm uncertain why it truncated.  I have seen that the samaccountname is limited to 20 -- but in the case with these account, the mail address is correct.  An example would be -- it truncates at (20 characters)?  Others accounts with problem are very similar.  

Thanks for in advance.
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Jason CrawfordTransport NinjaCommented:
Have you tried sending directly from OWA?  Do the emails just get stuck in the Outbox or bounce or what?
apsutechteamAuthor Commented:
Mailboxes are 'not found' because is truncates them to an incorrect mailbox name?  No, I have not emailed them directly.  For instance, -- becomes -- which isn't the mailbox name - so it isn't found.
Vidit BhardwajAdminCommented:
Do you get a NDR because I don't think character limit can be a problem here as it is 571 for email address and 64 for mail nickname attribute
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Vidit BhardwajAdminCommented:
I just realized you might get an NDR because of the email address it was finally sent to.

Ok as mentioned above sending through OWA we need to test it.
SysToolsData Expert - Recovery,Backup,MigrationCommented:
Hey ,
To know more, you can refer:

Hope the information helps you.

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apsutechteamAuthor Commented:
I figured out what my problem was.  Email were sent by Powershell script -  actually processing the members of a 'group' to send the emails.  Since the email attribute isn't returned from get-adgroup -- I was making the email address by appending the domain to the samaccoutnname.  Samaccountnames can't exceed 20 characters -- that's is were the truncation happened.  You wouldn't have had enough info to spot that ...
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