There are many details of which we need to take care when we set the DNN SMTP. Using the right settings combination in SMTP is very important.

Common SMTP setting

For most E-mail account, we need to provide SMTP Authentication information when we try to use SMTP server，so for most E-mail account, you should choose "Basic" under “SMTP Authentication:” and fill the "SMTP Username" and "SMTP Password"

Important! "Host Email" field under "Host Details" section in host settings menu must be modified to the Email address correspond to you SMTP. Such as your use smtp@163.com SMTP server, Host Email muse be yourusername@163.com.

SMTP Server and port: You can get the SMTP server address through you Email provider's help web page. Most time is "SMTP" "your email domain name", such as "smtp.163.com".

SMTP Authentication: choose "Basic"

SMTP Username: part before "@" symbol

SMTP Password: your password

GMail SMTP Setting

For Gmail,  one special thing you need to pay attention is: you must  check "SMTP Enbale SSL"，other settings are the same with common SMTP.

Because GMail use SSL，if you do not check SMTP Enable SSL, you'll get the error below:

There has been an error trying to send the test email. The error is:
The SMTP server requires a secure connection or the client was not authenticated. The server response was: 5.7.0 Must issue a STARTTLS command first. i6sm2749151tid.16

SMTP Setting of Catalook

Because Catalook do not support SSL，so Catalook can not use the SMTP server need to use SSL.