What does the message "mail rate limit exceeded" mean?

[Admin Dir at TASLA]

One of my employee's is having trouble sending email to the rest of us. He
keeps getting an error "451 mail rate limit exceeded -- try again later"
He has the same Outlook settings as the rest of us. But he keeps getting
System Administrator messages saying his message is undeliverable.

 

[VanguardLH]

One of my employee's is having trouble sending email to the rest of us. He
keeps getting an error "451 mail rate limit exceeded -- try again later"
He has the same Outlook settings as the rest of us. But he keeps getting
System Administrator messages saying his message is undeliverable.

So WHOSE mail server is this employee using? Ask that admin as to what
is their maximum messages-per-day quota configured in their anti-spam or
anti-abuse rules. Could also be a maximum mail-sessions-per-minute
quota.

Not an Outlook issue. The mail server doesn't like how many e-mails
have been sent by this particular sender or how many mail sessions they
try to generate within a short period of time. You'll need to contact
the admin of the mail server to find out what are their anti-spam
quotas.