Problem delivering mail when user submit unknown TLD

Hi.
First thank you for a great plug-in!

By accident I noticed what seems to be a strange bug, or misbehavior by Post SMTP. If it is not intended, but I don’t see why that could be.

I will try to explain.

I have a contact form where the user submits his email address. I use the email field as reply-address. So far so good, everything works and Post SMTP deliver the all mails.

If the user writes a misspelled but still potential valid address, it still delivers the mail and it’s content to me – as it should of cause.

But, if the user writes a misspelled TLD, Post SMTP don’t deliver the mail to me, but instead send a “Post SMTP email error” to the WP admin address with:

You getting this message because an error detected while delivered your email.
For the domain: my domain
The log to paste when you open a support issue:
Invalid “Reply-To” e-mail address “the usersubmitted address”

I don’t see why Post SMTP should not deliver the mail, just because it contains a reply-to information with a misspelled TLD? As long as everything else is correct. So I wonder if it is a kind of bug – intended behavior??

Kind regards from Thomas