Sender verify failed

RK-BZ

Member
Aug 8, 2016
7
1
3
germany
cPanel Access Level
Root Administrator
We have a problem with receiving e-mails via Microsoft 365. Our server partially rejects incoming e-mails since September 1st 2020.

We have now received a recommendation that maybe an update to Exim version 4.94 will help.

Could an update be the solution to the problem or is there another cause?

cPanel 90.0.5
Exim: exim-4.93-5.cp1186.x86_64
 
Last edited:

RK-BZ

Member
Aug 8, 2016
7
1
3
germany
cPanel Access Level
Root Administrator
Code:
H=mail-xxx.outbound.protection.outlook.com (EUR05-xxx.outbound.protection.outlook.com) [xxx]:57088 sender verify fail for <[email protected]>: mx08.domain.com [xxx.xxx.xx.xx] : SMTP error from remote mail server after RCPT TO:<[email protected]>: 550 5.7.1 Bounce attack signature verification failed.
H=mail-xxx.outbound.protection.outlook.com (EUR05-xxx.outbound.protection.outlook.com) [xxx]:57088 X=TLS1.2:ECDHE-RSA-AES256-GCM-SHA384:256 CV=no F=<[email protected]> rejected RCPT <[email protected]>: Sender verify failed
H=mail-xxx.outbound.protection.outlook.com (EUR05-xxx.outbound.protection.outlook.com) [xxx]:57088 Warning: "Detected session with all messages failed"
H=mail-xxx.outbound.protection.outlook.com (EUR05-xxx.outbound.protection.outlook.com) [xxx]:57088 Warning: "Increment slow_fail_block Ratelimit - mail-xxx.outbound.protection.outlook.com (EUR05-xxx.outbound.protection.outlook.com) [xxx]:57088 because of all messages failed"
 

keat63

Well-Known Member
Nov 20, 2014
1,854
226
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cPanel Access Level
Root Administrator
Personally, I'd suggest that the update of exim is a techs way of saying that they don't know what the problem is, so lets update first and rule that out.
However as @nixuser suggests, getting hold of the reject notification, message headers and log entries would be a good start.
Also, if not already, consider adding SPF and DKIM entries to your DNS.
 

cPanelLauren

Product Owner
Staff member
Nov 14, 2017
13,296
1,252
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Houston
The threads here may be helpful: