I'm in the beginning stages of IP Warming for my client, and the first week had a very high deliverability rate - 99%-100%. This week, we're experiencing around 84% deliverability with a very high number of block bounces reported.
The same email is going out (compared from last week to this week). The same sender profile is being chosen, the same IP address. I'm curious what might be causing this? I did extract the Bounce data to a flat file and it did not have any relevant information on there as to more details around the block bounce and what might be causing it. I've opened up a Salesforce Support Ticket to see if they could dig into it - but, does anyone here have any idea why this might be happening?
It appears that an SMTPBounceReason is:
5.3.2 (system not accepting network messages) resimta-po-28v.sys.comcast.net resimta-po-28v.sys.comcast.net 220.127.116.11 found on one or more DNSBLs, see postmaster.comcast.net/smtp-error-codes.php#BL000010";
Most of the SMTPMessages mention blacklists. But what is weird is that this was working 100% perfectly with the same email last week - I'm only sending between 4-7k emails a day for IP Warming (a lot less than usual, I know). I did cross reference the IP address with some blacklist sites and I can't seem to find any sites that have my IP blacklisted.