Mailing generating large number of bounces, reason is "Unknown bounce type"

[BuckyFullerInst]

Hi there. We've been using CiviSMTP for some years now, and there has always been the natural marginal bounce rate for each mailing. We recently moved our hosting service from a Bluehost shared account to one of their VPS servers, and now our mailings are generating a massive number of bounces, with the Bounce Reason "Unknown bounce type: Could not parse bounce email". It was 17% of the list with the last complete mailing we sent.

I went into the database and took all addresses off hold to refresh for subsequent mailings, and with the current mailing, the number of bounces is almost equalling the number of successful mailings. That would include the ones that should actually be bounces, but a large majority are still of the "Unknown bounce type: Could not parse bounce email" type. I'm not sure if this is a version issue, but it is seriously hampering the successful delivery of our emails. Our hope is that it is a version issue - We are rolling out with a totally new redesign of the site on D7, with a clean-up/migration of the CiviCRM database, in the next weeks, and it would be great if the problem went away with the new versions of Drupal, CiviCRM, and PHP (going from 5.2 to 5.4)

[alleyla]

Hello,

To clarify, is 17% your normal bounce rate for mailings and the unsuccessful mailing was around 50%?
Also how many mailings have you observed so far that resulted in ~50% bounce rate? was it only one time or can you reproduce it consistently?

We are going to need the following information to debug this issue:
- Your CiviCRM and Drupal versions
- date/time/timezone for the mailing that resulted in 50% bounces
- number of intended recipients for this mailing
- email us a few of the valid email addresses that bounced with the Bounce Reason "Unknown bounce type: Could not parse bounce email" to support@civismtp.com. Valid meaning you know that they worked and didn't bounce in previous mailings.


- CiviSMTP Support

[BuckyFullerInst]

Hi there! So we've gone ahead and put in a whole new CiviCRM install, to coincide with a wider refresh of our entire site. We're now up to Drupal 7.26, CiviCRM 4.4.3, and PHP 5.4.24. I went back through all of the CiviSMTP setup instructions, and all the connection tests check out. Great. I tried sending through a test mailing, going to 4 local email addresses on our domain, just to check if mailing is working. After submitting the mailing and running /civicrm/mailing/queue?reset=1, the mailing reports back as completed, but it appears that there have been no successful deliveries, but also no bounces either. What could be going wrong here?