Getting several warnings

Hi there,

Would appreciate any help you can give me on this issue.

When accessing /wp-admin, I am getting the following errors:

Warning: Illegal string offset ‘headers’ in /var/www/html/wp-content/plugins/global-smtp/global-smtp.php on line 224

Warning: Illegal string offset ‘headers’ in /var/www/html/wp-content/plugins/global-smtp/global-smtp.php on line 224

Warning: Illegal string offset ‘headers’ in /var/www/html/wp-content/plugins/global-smtp/global-smtp.php on line 230

Warning: Cannot modify header information – headers already sent by (output started at /var/www/html/wp-content/plugins/global-smtp/global-smtp.php:224) in /var/www/html/wp-includes/pluggable.php on line 1223

Can you help me with those?

What can I do at this stage?

The entire page is blank.

Cheers!

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