Not sure whether this is a bug, or a problem on my setup or the server.

But I have spent 3 days searching for solutions, testing, troubleshooting with my host support which was very helpful. But problem persists.

I upgraded (from 1.3.7 to 1.5.4) about a month ago, and the email was working perfectly on SMTPAuth after some struggle (see the thread that got me there: https://www.zen-cart.com/showthread....30#post1285030).

However, about a week ago, I suddenly started to see orders in the Admin CP that I did not receive copy of the email confirmations. I did testing, and found that now I am not receiving any email - account creation, order confirmation, contact us form email. I tested as a fake customer, and am not receiving any email as well.

I have tried different SMTP Auth setup, used different email accounts as the "send from" and the "SMTP Email Account Mailbox" with respective mail server login info. None worked. Invariably I get a green notice saying "email sent", and a red notice on top saying "Called Mail() without being connected".

I have been checking with the hosting server's support. They see nothing unusual on my account.

When I switch to PHP Email Transport method, I get same green "email sent", and then red error "Could not instantiate mail function.". In this case, the server support report the following PHP error: PHP Warning: Illegal string offset 'EMAIL_FROM_ADDRESS' in MYSTORE/includes/functions/functions_email.php on line 103, and the line's content in my file:
PHP Code:
if (!isset($block['EMAIL_FROM_ADDRESS']) || $block['EMAIL_FROM_ADDRESS'] == '') $block['EMAIL_FROM_ADDRESS'] = $from_email_address; 
The server PHP version is 5.4 and has not changed recently.

That's all info I can come up with. I need to fix this problem. Thanks a lot in advance for your attention.

Jeff