What does '530 must issue a STARTTLS command first' mean?

[Khc1313]

I am trying to send email from my outlook as I have been doing for 5 years
with the same email address, all of a sudden this week none of my outgoing
mail is being sent, yet I still receive messages. The system says: Unable to
send the message. Please verify the email address in your account properties.
The server responded: 530 must issue a STARTTLS command first.
Any help will be greatly appreciated. Thank you.

 

[Brian Tillman [MVP - Outlook]]

I am trying to send email from my outlook as I have been doing for 5 years
with the same email address, all of a sudden this week none of my outgoing
mail is being sent, yet I still receive messages. The system says: Unable to
send the message. Please verify the email address in your account
properties.
The server responded: 530 must issue a STARTTLS command first.
Any help will be greatly appreciated. Thank you.

Sounds like your mail provider has changed their requirements and is requiring
an encrypted SMTP connection now whereas before they weren't. Thi sis not
uncommon. Visit their web page and look up the settings they require for
Outlook.