ActionMailer - limit on number of recipients? - ruby-on-rails

Question

I've got Capistrano set up to send emails after deploying my RoR (2.3.8) application. I have a config/cap_mailer.rb file that basically looks like:
ActionMailer::Base.smtp_settings = {
:address => my,
:port => exchange,
:domain => server,
:authentication => settings,
:user_name => are,
:password => here
}
class CapMailer < ActionMailer::Base
def deploy_notification(cap_vars)
recipients cap_vars[:notify_emails]
from 'deploy#my.org'
subject "New app!"
body "Deployed application...blah blah blah"
end
end
Then, in my deploy.rb file, I have the following:
require 'config/cap_mailer.rb'
...
desc "Email recipients of deployment"
task :notify do
puts " * Sending notification email"
set :notify_emails, ["test1#my.org", "test2#my.org", etc.]
CapMailer.deliver_deploy_notification(self)
end
Now this all works fine and dandy......until I put more than 7 email addresses in the :notify_emails array. Up to 7 works fine, but when I put 8 or more (all valid addresses), the email gets screwed up a little bit (still goes through to the first 7, at least). Looking at the email header, it shows that it is cutting off the 8th (and 9th, 10th, ...) address from the 'To:' and putting it in the message body.
HEADER:
thread-index: AcyaZxlga08L9p35QYKJ22aiGG2zeA==
Content-Class: urn:content-classes:message
Importance: normal
Priority: normal
X-MimeOLE: Produced By ...
Received: from exchange.my.org ([ip address]) by ...; Thu, 3 Nov 2011 14:28:08 -0600
Date: Thu, 3 Nov 2011 14:28:08 -0600
From: deploy#my.org
To: test1#my.org,
test2#my.org,
test3#my.org,
test4#my.org,
test5#my.org,
test6#my.org,
test7#my.org
HEADER:
BODY:
test8#my.org
Message-Id:
<4eb2f95816341_135ff800c21ac130#my_box.local.tmail>
Subject: New app!
Mime-Version: 1.0
Content-Type: text/plain; charset=utf-8
Return-Path: deploy#my.org
X-OriginalArrivalTime: 03 Nov 2011 20:28:08.0494 (UTC)
FILETIME=[19601CE0:01CC9A67]
Deployed application...blah blah blah
BODY:
In addition, the subject does not appear on the email, even though the "error text" in the message body shows the correct subject.
Does anyone have any idea why this is happening? What is it about having 8 or more recipients that breaks it? I've Googled around and can't find anything about ActionMailer having a limit on the number of recipients (even if there were, that's a small limit). Is there something I'm missing? Any help is appreciated! I really need to be able to send to 8 or more recipients.
UPDATE: Setting the recipients directly with an array of 8 or more addresses still breaks things, so this clearly seems like a problem with ActionMailer and not Capistrano.
recipients ["test1#my.org", "test2#my.org", "test3#my.org", "test4#my.org",
"test5#my.org", "test6#my.org", "test7#my.org", "test8#my.org", "test9#my.org"]

Answer 1

The 7th email address is not followed by a comma, which could be the problem. Try passing a string to recipients, like cap_vars[:notify_emails].join(','), with no newlines.

Answer 2

Try passing a string to recipients without commas (there have been reports of commas as a problem), like:
cap_vars[:notify_emails].join(' ')

Answer 3

With all respect some simple things that you might overlook in debugging difficult errors:
If its mail server related install it on another production server? If you not sure it is the mail server acting up looking for another error may be of no help.
Try upgrade rails / ruby ? Perhaps its a bug in the code