3 small Windows plesk error's that needs fixing.

Hello, I got 3 small problems on my Windows plesk server that needs fixing, 1; SMTP error from GMAIL to all the domain e-mail on my vps i get; "from gmail to me (i just got this mail send to me) this error "Onderwerp: Delivery Status Notification (Failure) Delivery to the following recipient failed permanently: dennis**.nl Technical details of permanent failure: Google tried to deliver your message, but it was rejected by the server for the recipient domain [login to view URL] by hetoffensief.nl. [**.**.**.**]. The error that the other server returned was: 550 This mail server requires authentication (1) when attempting to send via this SMTP (submission) port. ----- Original message ----- "" and if i send to some e-mail adresses with there own domains; " MailEnable: Message could not be delivered to some recipients. The following recipient(s) could not be reached: Recipient: [SMTP:****.**] Reason: Remote SMTP Server Returned: 550 Access denied - Invalid HELO name (See RFC5321 4.1.1.1) " 2; whenever i install wordpress i get the error with most costum theme/plugin's i buy on themeforest; ""Internal Server Error The server encountered an internal error or misconfiguration and was unable to complete your request. Please contact the server administrator to inform of the time the error occurred and of anything you might have done that may have caused the error. More information about this error may be available in the server error log. Web Server at ****.nl" and 3th; i want to import a database but i get the error: "#1273 - Unknown collation: 'utf8mb4_general_ci'" i need this fixed asap.