Mail Shield Conflicts with Outlook 2013 and SMTP.charter.net -- can't send

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Apparently the recent update broke my email connection to my ISP SMPT.charter outbound mail server.  I spend 2 hours with Charter.net and 2 hours researching the problem with no results.

The Outlook 2013 error message is:
Sending reported error (0x800CCC0F)  The connection to the server was interrupted.  If this problem continues, contact your server administrator or Internet service provider (ISP).  The server responded: 452 4.1.1 nbto: 11 too many rcpts 10E2210

As I said, Charter was of now help--still can send with there web based email.  I have verified all other email settings in Outlook 2013.  I created a new profile that generated the same errors.

The only way to eliminate the error is to turn AVAST Web Shield OFF--then everything works normally.  I even unchecked the "Scan Outboud Email" box, but that still generated the error above.  Note the error changes where the number after nbto: is either 1 or 11.  Occurs with 1 or more email addresses in the "To:" field.

I've spent 8 hours on this problem and still can't fix it==H E L P ? ? ?

Thanks in advance.

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There has been SO many topics on email issues over the years.  A lot of times it is improper install of the Avast Outlook plugin.
I would do a "clean" uninstall and new install of Avast.
Make sure to use the Avast Unistaller util.......else you may not remove everything that is causing issue.
https://www.avast.com/uninstall-utility

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Thank you for the suggestion.

I followed your instructions and my email accounts are now working again.

However, I have a problem that I have had in the past resurface.  Now, during the night when email is coming in, about 1 in 10 emails have the subject line modified with non-alphanumeric ASCII characters.  When I look at these emails with my webmail interface, the subject lines are fine--no strange characters.  I know last time I had this problem AVAST was to blame; but I failed to keep the emails related to how I cured this problem.

Further assistance would be appreciated.  Thank you.