The system site_name config value is used as the from name to send emails. When the site name contains special characters (like an HTML br tag), there is an error in the sending of the email. This may be a core issue, but it may still be possible to prevent the problem here?
This is the error recorded in the watchdog table under symfony_mailer_lite:
An attempt to send an e-mail message failed, and the following error message was returned : Email "br>Security"
Change site name to something like: My
Site
Run strip tags from site name before setting it to the from address header.
Active
2.0
Code
I don't think stripping tags will work, but I've come up with something else that might. Please test the MR, which is also available in this patch:
https://git.drupalcode.org/project/symfony_mailer_lite/-/merge_requests/23.patch