I'm working on optimizing our SPF record to fix email deliverability issues. We’ve had 5x the number of undelivered emails in June, July, and August, which coincides with issues I've seen other users raise both here in the forums and on Reddit. We send out about 7500 emails with invoices per month and average ~50 rejections. That number has risen to ~250 the last 3 months. Most errors are "Permanent Failure: Other undefined status".

I’ve gone through all the email troubleshooting and our initial DKIM, DMARC, and SPF checks all pass. However, one SPF testing tool I was using mentioned 5 NetSuite subdomains related to “include:sent-via.netsuite.com” were pushing above the 10-lookup SPF limit when combined with other domains are company uses. I'm guessing this is maybe causing the issues?