Alleluia!  From another post on this forum, THIS WORKS:

Activate Internet Options|Sending (SMTP) Menu entry .Highlight the

SMTP definition you're using and hit the Edit button.  In the resulting

dialog, hit the Security tab. In the first section hit the middle radio

button(Use STARTTLS).  In the second section, activate the third option

(Login using a POP3 username and password, and enter the POP3 definition

you're using in the edit box.

OK out of the dialogs and sending mail should now work. 

I woke up this morning and discovered suddenly I can't send!

Windows 10.

Everything was working fine yesterday and for some years.

Was using Pegasus 4.70, tried installing 4.71, made no difference.

Problem appears to be that some software thinks I didn't STARTTLS, but the handshaking dialogue clearly shows it was just started!  Here below is the dialogue:

14:05:24.266: --- 9 Apr 2016, 14:05:24.266 ---
14:05:24.266: Connect to 'smtphm.sympatico.ca', timeout 30 seconds.
14:05:25.322: >> 220 mtlspm01.bell.net ESMTP server ready Sat, 9 Apr 2016 14:05:22 -0400
14:05:25.326: << EHLO [192.168.2.11]
14:05:25.384: >> 250-STARTTLS
14:05:25.384: >> 250 OK
14:05:25.398: << MAIL FROM:<ewraven1@sympatico.ca>
14:05:25.458: >> 530 Must issue a STARTTLS command first

Help?

Eleanor White, Ontario, Canada