SMTP Size Limit Type constants specifies the size limit of an SMTP resource.
SmtpSizeLimit_LocalPart (0) - Maximum length of user name or the local-part in the address specification. Default 64 characters.
SmtpSizeLimit_Domain (1) - Maximum length of domain name. Default is 255 characters.
SmtpSizeLimit_ReversePath (2) - Maximum length of reverse path or email address of sender. Default is 256 characters.
SmtpSizeLimit_ForwardPath (3) - Maximum length of forward path or email address of recipient. Default is 256 characters.
SmtpSizeLimit_CommandLine (4) - Maximum length of the SMTP command line (including the CRLF). Default is 512 characters.
SmtpSizeLimit_ReplyLine (5) - Maximum length of the SMTP reply line (including the CRLF). Default is 512 characters.
SmtpSizeLimit_TextLine (6) - Maximum length of a text line in a message (not including the leading dot). Default is 1000 characters.
SmtpSizeLimit_RecipientsBuffer (7) - Minimum
number of recipients that must be buffered. Default is 100 recipients.