[Zope] sendmail with dtml-var

[Joshua Newman]

I made a variable 'mail_group' which appears in <dtml-var REQUEST> as: 
['first last <person@here.com>','first2 last2 <person2@there.com>']

and I want to use <dtml-sendmail>  so I have:

<dtml-let addr="_.string.join(mail_group,',')">
<dtml-sendmail mailhost="MailHost">

To: <dtml-var addr html_quote>
Subject: Feedback from somewhere
from: trying@somewhere.com
Comments:<dtml-var comments>

</dtml-sendmail>
</dtml-let>


But I'm getting totally impenetrable errors:

<dtml-var addr html_quote> renders perfectly to:
first last <person@here.com.,first2 last2 <person2@there.com>

and if I cut and paste the above line to the 'To:' field, mail is sent
perfectly.

BUT when i run the above sendmail script I get a page that says only: 
{'first': (550, '5.1.1 ... User unknown')}

If there is just one name in 'mail_group' I get an even weirder page:

{'f': (550, '5.1.1 ... User unknown'), 'i': (550, '5.1.1 ... User
unknown'), 'r': (550, '5.1.1 ... User unknown'), 's': (550, '5.1.1
... User unknown', 't': (550, '5.1.1 ... User unknown')} 


I am totally perplexed.  And SUPER frustrated.
Can someone tell me why this is and how to fix it if possible.

thanks 
joshua


p.s. if I use 
To: <dtml-in mail_group><dtml-var sequence-item><dtml-var addr html_quote><dtml-unless sequence-end>, </dtml-unless></dtml-in>

I get an error like:
Error Type: TypeError
Error Value: len() of unsized object

which I think is because of trailing spaces though I can't see any...