550 5.7.1 authentication is required

[chencong]

When my forum try to send mail, It always return this error: 550 5.7.1 authentication is required. How to fix it?

[Kindred]

well, you do need to provide some actual information...

what form of mail is your forum attempting to use?   SMTP or phpmail?
If STMP did you add the correct authentication information?

What version of SMF?

[chencong]

well, you do need to provide some actual information...

what form of mail is your forum attempting to use?   SMTP or phpmail?
If STMP did you add the correct authentication information?

What version of SMF?

SMTP with a correct authentication Informatio, latest version.

[Kindred]

latest is never an actual version....

and, I think that you are incorrect, as is demonstrated by the error message - your authentication information is NOT correct.