I sent a newsletter to 400+ subscribers last night (at 180 per hour). I use WP Mail SMTP plugin to handle the sending via (paid) Titan email account through our host (Hostinger).
Test emails from your plugin work. Your plugin says that 436 of 436 newsletters were sent.
I received my copy of the newsletter. The WP Mail SMTP debug log shows 30 error messages showing “Mailer: Other SMTP
SMTP Error: Could not connect to SMTP host.” I know what the error itself means. What does that mean in regard to the emails I was sending? I’m trying to figure out what those 30 errors mean as relates to the number of recipients that may not have received the newsletter. Do you have any information regarding this? Do you pass each newsletter off to the SMTP account which then connects to the email server and sends that one newsletter? Or do send x newsletters per y minutes (where “y” is set by a cron job or something that runs every few minutes and “x” is # of emails per hour divided by the cron interval – so a cron that runs every 5 minutes would send (180/12 (60/5=12) = 15) 15 newsletters in a batch so SMPT plugin would log in the mail server and send 15 emails. I will likely have to pass this question on to WP Mail SMTP, but first I want to know how you send the newsletters to the SMTP plugin.