For Australian users: high hard bounces from Bigpond addresses?

[KevinTruong]

Have any other users in Australia dealt with a high number of hard bounces from Bigpond addresses?

We have a recurring issue where Bigpond throttles our sends at a certain volume, meaning a proportion will be delivered successfully but then the remaining will be held as suspected spam, eventually getting hard bounced. This doesn't happen on smaller sends but does when it gets into 40-50k+.

We have workarounds of breaking them up into smaller volumes and spreading them out across different times, which seems to work ok, but wondering if there's a more sustainable solution out there? 

We use the Everest deliverability tool to check our emails and it never flags anything, so it does not appear to be related to the content of the emails but purely about the volume.  Our SPF/DKIM is set up and working too. We don't have this issue with any other domains. The pattern is never consistent either as we can see the same address bounce one day then work the next.

Some related links I found https://support.google.com/mail/thread/228225650?hl=en&msgid=228512364 

[SanfordWhiteman · Accepted solution]

We’ve encountered this problem, not just with Bigpond but a bunch of shops that place hard daily limits, no matter how engaged their end users are.

Our solution has been to run a private outbound mailserver (smarthost) for those domains, using SRS encoding to route via the private server. That server deliberately trickles mail into the destination domain over the course of a few days.

Naturally, this won’t work if your daily volume is consistently over their limit — but then you’re almost surely emailing too much!