mail() truncates message on full stop between two newlines

Description

The following code:

<?php
mail("myself@mydomain.com", "Subject whatever", "Foo bar\n\nWhatever\n\n.\n\nLorem ipsum dolor sit amet");

Resulted in this email body being sent:

Foo bar

Whatever

(not sure whether with or without the \ns at the end and how many of them)

But I expected this output instead:

Foo bar

Whatever

.

Lorem ipsum dolor sit amet

I know that a line with only a full stop is how the email body is terminated in the SMTP protocol, but this is not the SMTP protocol, this is a php function that takes a message and sends it via email. If the caller is supposed to encode the message the way it would be encoded in the SMTP protocol, the docs should say so; but again, that would be stupid.

PHP Version

8.0.12

Operating System

debian 10

Comienza localizando la implementación de mail() de PHP y la ruta que serializa los cuerpos de los mensajes para el transporte de correo local. Reproduce después el ejemplo proporcionado para PHP 8.0.12 y añade o actualiza una prueba de regresión para que se conserve una línea que contenga únicamente un punto y se envíe el cuerpo completo esperado.