What do you mean you checked your server and it shows no mail? Please while sending mass mail open your database via phpmyadmin, do the massmailing, righ after that go to the opened beforehand ow_base_mail table and refresh it, see if the mails are there and goes out, if there are no mails, your cron jobs are not properly configured, if they go out from the table this means something is wrong with the mail server. 

Also, please enable debug mode and go to www.yourdomain.com/ow_cron/run.php - what do you see in the browser? 

I have two Oxwall sites. My email is bombarded every hour with "Undelivered mail returned to sender" emails from both Oxwall sites. I have many other sites that are powered by wordpress, and they send email just fine. Why am I having all mail sent by my Oxwall sites bounce and come back to my email as return to sender?

This is the mail system at host (localhost).

 

I'm sorry to have to inform you that your message could not be delivered to one or more recipients. It's attached below.

 

For further assistance, please send mail to postmaster.

 

If you do so, please include this problem report. You can delete your own text from the attached returned message.

 

                   The mail system

 

<www.chix_magnet27@yahoo.com>: host mta5.am0.yahoodns.net[98.138.112.33] said:

    554 delivery error: dd Sorry your message to www.chix_magnet27@yahoo.com

    cannot be delivered. This account has been disabled or discontinued [#102].

    - mta1171.mail.ne1.yahoo.com (in reply to end of DATA command)

go to http://www.mail-tester.com/ ;
copy the email addy 
go admin invite users 
paste that addy n send the go back mail tester n check the problems 

fix the problem it says 

as to the returned mail you have 

have a look the addy its a url not mail addy 

www.chix_magnet27@yahoo.com

so i am guessing ur site is full of spammers and u must had site set to not confirm emails 
or you have inporteded a bodge profile list 

if it was working fine on 1.6   and problem is since 1.7 
go ur database n look ow_users and look the emails and see if they have the www in the front 
if they do u will have to manual remove the www
if they dont something is adding the www to them before they are sent 

have you scanned the server with clamiv  virus scanner have you good virus scanner on computer you use to ftp stuff to the server

+1 to Chris_W . Get rid of non existing/spammer emails and everything will be ok.

Thank you all for your suggestions on this issue. It seems that what ever was causing this problem has corrected itself. I have noticed there is a delay in getting the mail but it is now working. Once again Thank you all for your input.

Sincerely and respectfully,
James