When I tried to upload a file, it gave me this error. I just upgraded Moodle from 1.9.11 to 2.2.1

This is just an except from the error message.

ERROR: Invalid JSON string

SMTP -> get_lines(): $data was ""
SMTP -> get_lines(): $str is "220 *************************************
"
SMTP -> get_lines(): $data is "220 *************************************
"
SMTP -> FROM SERVER:220 *************************************

SMTP -> get_lines(): $data was ""
SMTP -> get_lines(): $str is "250-mx.google.com at your service, [41.223.136.6]
"
SMTP -> get_lines(): $data is "250-mx.google.com at your service, [41.223.136.6]
"
SMTP -> get_lines(): $data was "250-mx.google.com at your service, [41.223.136.6]
"
SMTP -> get_lines(): $str is "250-SIZE 35882577
"
SMTP -> get_lines(): $data is "250-mx.google.com at your service, [41.223.136.6]
250-SIZE 35882577
"
SMTP -> get_lines(): $data was "250-mx.google.com at your service, [41.223.136.6]
250-SIZE 35882577
"
SMTP -> get_lines(): $str is "250-8BITMIME
"
SMTP -> get_lines(): $data is "250-mx.google.com at your service, [41.223.136.6]
250-SIZE 35882577
250-8BITMIME
"
SMTP -> get_lines(): $data was "250-mx.google.com at your service, [41.223.136.6]
250-SIZE 35882577
250-8BITMIME
"