Hi,
This problem is similar to mine but the solution doesnt work for me:
After an upgrade to 2.6 no emails are send after comments posts or backups. The sending of emails does not fail, they are simply not send. My eventviewer doesn’t log any action to send an email after a comment is posted or when a backup is made.
When i try to send myself an email with (lost password function) is get the folowwing errormessage: Fatal error: Cannot redeclare class PHPMailer in …./wp-includes/class-phpmailer.php on line 1517
Anyone has a clue?