Why am I getting this message " An error occurred Cannot send Message (Email Recipient not accepted by the server)

I use eM for two email accounts. Both are from the same provider and the SMTP and POP parameters are identical.  Several days ago I lost the ability to send emails from one of the accounts per the error message in the title

Hi Hank,
please next time the error pops up click the third tab in the same window as the error message (titled Log) and copy the content of it here.
It should contain more details about the error,

Regards,
Olivia

Here it is

8:17:18 AM henrywisniewski@frontier,com [SMTP] Connecting: To henrywis …

8:17~18 AM henrywisniewski@frontier,com [SMTP] Connected: To henrywis. …

8:17:18 AM henrywisniewski@frontier.com[SMTP] Sending messages

8:17:18 AM henrywisniewski@frontier.com[SMTP] Sending messages: Reci

8: 17: 18 AM "4.7.1 <thenyskis@frontier.com >: Recipient address rejected: …

8:17:18AM "

8:17:18 AM MaiIExceptions.ItemOperationException: Cannot send messag …

8:17:18 AM henrywisniewski@frontier.com[SMTP] Disconnected: From hen …

8:17:18 AM henrywisniewski@frontier.com[SMTP] Disconnected: Done

Hi Hank,
could you use the ‘Ctrl’ + ‘A’ shortcut to select full content of the log and then copy it out (Ctrl + C and the Ctrl + V)? I’m afraid there seems to be parts of the log missing.

Regards,
Olivia

10:03:03 PM henrywisniewski@frontier.com [SMTP]  Connecting: To henrywisniewski@frontier.com
10:03:03 PM henrywisniewski@frontier.com [SMTP]  Connected: To henrywisniewski@frontier.com
10:03:03 PM henrywisniewski@frontier.com [SMTP]  Sending messages
10:03:03 PM henrywisniewski@frontier.com [SMTP]  Sending messages: Recipient address ‘thenyskis@frontier.com’ not accepted due to the following reason:
10:03:03 PM     "4.7.1 <thenyskis@frontier.com>: Recipient address rejected: henrywisniewski@frontier.com exceeded hourly recipients threshold… See http://postmaster.frontiernet.net
10:03:03 PM "
10:03:03 PM   MailExceptions.ItemOperationException: Cannot send message (Email recipient not accepted by the server.)
10:03:04 PM henrywisniewski@frontier.com [SMTP]  Disconnected: From henrywisniewski@frontier.com
10:03:04 PM henrywisniewski@frontier.com [SMTP]  Disconnected: Done

Hi Hank,
seems like your mail server is blocking your messages, because you exceeded the hourly limit of sending messages.
Checking their error page - http://postmaster.frontier.com/error… - I’d suggest trying the Solution for ‘Message rate limit exceeded’ section and check your machine for viruses or trojans; your computer may be sending out spam without your knowledge.
If that is not the case, contact your mail provider (Frontier) about the issue, as they are the ones blocking your outgoing message.

Regards,
Olivia