There was an error trying to send your message. Please try again later

I received the following message:
“There was an error trying to send your message. Please try again later”, when sending a message from Contact Forms using Contact Form 7.

I managed to temporarily resolve the problem by changing the
Email from address in the Email Settings from:
[your-name] <[email protected]>
to
[your-name] <[email protected]>

Email-Alias was just an email alias to the real email address: Email-not-Alias.

Note, the email/alias addresses here are just descriptive i.e. not the real one.

I could use the Alias form until the 12th. Sep. 2019, then something suddenly changed.
Wordpress, version 5.2.3 is installed – I am not sure when this version was installed.
PHP, version 7.2 is installed – this version has been installed for several months now.

I am not sure if this is problem with the plugin: Contact From 7 or something in WordPress.

I hope it will be possible to use email aliases again as the Email-From address.
Until then, do I hope this help somebody else having the same problem.

The page I need help with: [log in to see the link]