2417443 - Inbound error "554 Transaction failed"

After a system upgrade, it is being noticed, that the Inbound e-mail queue in transaction SOIN do not receive any e-mails. This is an abrupt situation with no manual modification.
All Inbound e-mail settings are in place:

• SMTP host and port in ICM are configured;
• SAPConnect virtual host is configured;
• Inbound user is assigned to SAPConnect virtual host and there are no password locks;
• The correct authorizations are assigned for service user;
• Telnet tests return "554 Transaction failed".

• SAP Netweaver Release Independent;
• Third-party external mail server.

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