No emails to experts

What do your server's mail logs show? I would first check your MTA log to see what is happening. If no errors are showing there, then check your IMAP/POP server log.

Hopefully one of those logs should show you where the messages are gettign dropped. You can also check the queue directory for the MTA to see if the mail you are attempting to send is stuck there. The same holds true for the mailbox directories, you will need to know if you are using mbox of /Maildir style mailboxes to figure out where the possible mail is.

Also, please see if the receiving mail program is issuing any messages. Others are getting the email, so the last thing I would check would be the code.

I'm not saying that it is something on your server, just that your server's mail logs are the first places I would look when troubleshooting this issue.

You may want to try the devel module and see if it can trap any error messages returned by your SMTP server, if there are any.

I haven't used that module much so I do not know if it is capable of doing the above.

Another route to check would be to send a test email to one of the recipients from the same SMTP server that Drupal is connecting to and see if it goes through.

Can Bluehost work with you, e.g check the logs for you, see if the sent mail is sitting in your SMTP server's mailqueue, etc, when you try to send the email?

The MTA and IMAP/POP logs are the receiving mail programs, if I understand what you mean by receiving mail program properly. It is not looking through code. Figuring out what is going on when things aren't working as expected is one of the reasons programs have log files. Looking at those logs are the first thing that should be done when things aren't working as expected. Not doing so will usually lead to wasting a lot of time on speculation of what the problem may be.

The logs should also be inspected in the order specified, e.g. the MTA program's log and then the IMAP/POP program's log since that is the order that mail will work it's way through the system. If the recipient mailbox isn't on a domain for which you manage mailbox's you will not need to look at your IMAP/POP program's log, since it won't be involved in it.

If the MTA program is accepting the connection and sending it on, then I would test using a recipient whose mailbox I manage so I can see what is happening on that end.

FYI:
Email sending/receiving on the server side breaks down into two major segments, SMTP and most commonly IMAP4/POP3. The reality of mail handling is usually more compicated, but those two parts are the minimum required for a 'mail server' properly.

SMTP is Send Mail Transport Protocal and is concerned with the sending and relaying of mail and the program that handles it is your MTA, mail transfer authority, most likely Sendmail or Postfix on Linux. This is what your email client connects to when you want send an email.

IMAP4/POP3, usually referred to IMAP/POP are the most common mailbox protocals. This is what your email client connects to to check on/receive email. When an email is received, the MTA accepts it, if acceptable, and hands it off to the program that is responsible for placing it into the recipients mailbox.

Okay. I'm marking this as postponed. If you find it not to be a problem with your new host, please mark it as "By design" (not "closed").

Thanks for the update. And just a warning, the mail is currently broken in the 6.x version.

Just as an addendum to this, we saw the same problem when revisions were turned on for FAQ items. When we turned that off, the emails started going out. Not critical for us, but I thought this information might help if someone else encounters the same problem.