[horde] Imp upgrade smtp error

[Gary Witscher]

I am unable to send mail since my upgrade to webmail 5.1.

I use google smtp and am getting this error:

2013-06-06T04:20:24+00:00 ERR: HORDE [imp] Failed to set sender: 
xxxxxxxx at gmail.com [SMTP: Invalid response code received from server 
(code: 530, response: 5.5.1 Authentication Required. Learn more at
5.5.1 http://support.google.com/mail/bin/answer.py?answer=14257 
fr1sm70921385pbb.26 - gsmtp)] [pid 9941 on line 1068 of 
"/var/www/horde/imp/lib/Compose.php"]

I've followed the instructions referred to, but the problem persists. 
I'm using the same Mailer settings I have been using since I've started 
using Horde. These settings work when I use Thunderbird or Sylpheed. 
I've tried enabling Debug in my Horde log, but I don't see anything more 
than the message above that seems applicable to sending messages.

I'm at a loss as to how to debug this, any help would be appreciated.

TIA,
Gary