You are trying with your Gmail mail server and it’s blocked from Gmail not form your host.
Enable Gmail less secure apps into your Gmail account.
If you want to allow access anyway, follow these steps:
1) Go to the Less secure apps section of your Google Account.
2) Turn on Allow less secure apps. If you don’t see this setting, your administrator might have turned off less secure app account access.
and use this setting: Outgoing Mail (SMTP) Server: smtp.gmail.com.
Use Authentication: Yes.
Use Secure Connection: Yes (TLS or SSL depending on your mail client/website
SMTP plugin)
Username: your Gmail account (e.g. [email protected])
Password: your Gmail password.
Port: 465 (SSL required) or 587 (TLS required)