Akismet blocks new user email outside of host’s domain

Am using Akismet 4.1.2 on WP 5.2.2.
When Akismet is active and a new subscriber is created by an admin, the email that should be sent to that subscriber with the link to set a password is not sent if the domain of that email address is different from the domain of the WP server.
Steps to reproduce the problem:
0) WP is at http://www.mysite.com
1) login as an admin and create a new user as a subscriber with email address [email protected]
2) WP sends the email to that address with the link to reset the password (i.e., all is OK)
3) create a new user as a subscriber with email address [email protected]
4) WP does NOT send the email to that subscriber (and the email is NOT is a spam folder, either)
5) deactive Akismet
6) create a new user as a subscriber with email address [email protected]
7) WP sends the email to that address with the link to reset the password (i.e., all is OK)
8) reactivate Akismet
9) once again the email is not sent

Other notes:
– AFAICS, there are no custom functions that concern the send of any email by WP
– every other type of email functionality that I use works fine
– I have no plugin installed that is specifically designed to handle email sent by WP
– I don’t see anything in the php error log that seems to be relevant to this issue
– I don’t see anything in the email server configuration that might be related to this issue, especially given that the email is sent whenever Akismet is deactivated.