Is Send Email function a cron job? Do I have to wait for the page to finish?

When I send an email via ZenCart, whether through the coupon or just the Send Email function, must I wait for the process to finish or is this submitted as a job that will finish in the back ground, so that I can navigate away from the sending email page to work on something else?

I am asking because I have over 1,000 customers that I send emails to on a regular basis. It takes so long that I receive various errors when the screen automatically refreshes after about 3 to 10 minutes.

With that many recipients, I would consider using a third-party mailing mod, like MailChimp.

Sending different groups of customers an email is very helpful for marketing, but using a third party mod would make this very difficult. This isn't just an email blast, but targeted marketing to customers who haven't bought from the store before. Any knowledge as to if sending an email is a job or if I have to wait for the send mail page to finish processing, which as I mentioned, generates an error nearly every time?

I believe it sends at script end as I usually get my emails immediately.

What Email transport method are you using? Sendmail, SMTP, PHP?

PHP sends when the script finishes. SMTP sends directly to the recipients, Sendmail 'spools' the mail which is sent at regular intervals that are defined by the host.

Cheers
RodG

I am currently using smtpauth. Which option(s) is best for emailing larger number of customers?
PHP
sendmail
sendmail-f
smtp
smtpauth
Qmail

sjdeines:

I am currently using smtpauth. Which option(s) is best for emailing larger number of customers?
PHP
sendmail
sendmail-f
smtp
smtpauth
Qmail

I'd be inclined to try sendmail, sendmail -f or Qmail (whichever is supported by your host).
I make no promises that this will improve matters though (it could even introduce other problems).
As Stevesh has suggested, with as many recipients that you have, a 3rd party mailing mod would be your best option.

Cheers
Rod

You can easily segment your list in Mailchimp to target groups of subscribers. Read these threads:

http://connect.mailchimp.com/integrations/zen-cart-marketing-suite
http://connect.mailchimp.com/integrations/zencart
http://www.zen-cart.com/downloads.php?do=file&id=425