There is an apparent listing on spamhaus
blocking a large portion of our postfix email sending and receiving:
https://check.spamhaus.org/listed/?searchterm=70.112.146.183
Somehow we were affected by samhaus yesterday and are just
getting the attached error on all of our emailing. The spamhaus website says contacting our ISP is the only way of correcting it. A copy of the error msg received is below...
Your message did not reach some or all of the intended recipients.
Subject: test
Sent: 11/3/2022 12:50 PM
The following recipient(s) cannot be reached:
iPro Real Estate on 11/3/2022 12:50 PM
Server error: '554 5.7.1 Service unavailable; Client host [70.112.146.183] blocked using sbl.spamhaus.org; Error: open resolver; https://www.spamhaus.org/returnc/pub/35.80.35.103'
This is the same issue I am experimenting with since Wednesday morning around 10:30 AM, I have lost a lot of emails from trusted companies and people with that I work for many years, I have felt frustrated trying to resolve this issue and now I noticed that AWS launched on Wednesday, Nov 2 a "new" security group for instances (Mail server), I have tried to delete this new security for my mail instance but says "you can't delete" how to fix this issue.?
The issue actually did start at about the same time Wed for me as well. Also, usually sending and receiving numerous (100s) of reputable business related emails daily. Although, do receive a lot of spam emails that I have to weed out...
I checked the EC2 Instance for added security groups as mentioned, but nothing on my end.
Figured out that the postfix main.cf just needed to be revised to remove restrictions.
Have you resolved the issue? do you remove all restrictions or any particular ones?