#35 Email date header uses incorrect format

The date format used for Aggie's email date header is
wrong. This causes MUAs I tried it with (Outlook and
Mozilla Thunderbird) to believe that all emails were
sent at midnight. Change line 422 of SmtpBatchMailer.cs
from

SendRequest(ref buf, header.Encode( "DATE", "{0}",
DateTime.Now.ToLongDateString()));

to

SendRequest(ref buf, header.Encode( "DATE", "{0:R}",
DateTime.UtcNow));

to fix the problem.