When the number of concurrent connections in avast! Internet Mail scanner is reached, you may recieve following error message:

421 concurrent connections limit in avast exceeded

Limit of concurrent connections in avast! Internet Mail is common for all threads scanned by this provider - both e-mails (protocols SMTP, POP3 and IMAP) and news (protocol NNTP). This problem can be caused by any application capable of opening more concurrent connections using the protocols listed above (i.e. a legal 'news leecher' application or a mass-mailing virus).

• Default value of concurrent connections in avast! Internet Mail provider is 20. This parameter can be changed in avast4.ini file, where under section:
  
  [MailScanner]
  
  ...following line need to be added:
  
  MaxConnections=decimal_value
  
  But at first try to find software application capable of opening more concurrent connections using the protocols listed above in details (usually the reladed process is listed in the error message) - then you can change its configuration or set a required value for MaxConnections variable.
  
  Note:
  Default installation path for avast4.ini file is:
  
  C:\Program Files\Alwil Software\Avast4\Data
  
• Another possible reason for this error is a incompatibility with an installed firewall (infinite loop opening new connections...). In that cases try to check firewall configuration according to its documentation, or contact your firewall vendor for further assistance.

avast! Home Edition 4.8 (and prior releases of version 4.x)
avast! Professional Edition 4.8 (and prior releases of version 4.x)

Operating systems:

Microsoft Windows NT 4.0 Workstation
Microsoft Windows 95
Microsoft Windows 98
Microsoft Windows ME
Microsoft Windows 2000 Professional
Microsoft Windows XP Home / Professional / Media Center Edition
Microsoft Windows Vista Starter / Home Basic / Home Premium / Business / Enterprise / Ultimate
Microsoft Windows 7 Starter / Home Basic / Home Premium / Professional / Enterprise / Ultimate