The problem is solved! I claimed here and to Frontier support that nothing had changed, but I had forgotten - I played with my modem's settings and, finding the firewall to have "too low" security, I upped it. That apparently blocked some ports, as was suggested above. I think that on my computer my anti-virus is providing the firewall. Yay!

I was disappointed that Frontier, my ISP, claimed that Pegasus isn't supported, though I told them it was just a POP3 client. I worked with several folks - 2 of them gave u pretty quickly and never even suggested looking at the modem settings. I'm so glad I got it resolved! Thanks, all. 

I have been using the same ISP for years and have my smtp configured as they have specified. But suddenly as of late last night, outgoing mail isn't going. I get the smtp error as below. All the security settings are as they were - nothing changed on my end. My ISP, Frontier, claims that Pegasus isn't supported, yet it is just a POP3 client and I can't see how the problem can be from the client when nothing changed from when email was sending (I am still receiving email). I rebooted and there is no change. I am including my Pegasus Mail 4.70 for Windows information below. Help! Thanks.

           Dilip

13:01:56.719: --- 16 Mar 2015, 13:01:56.719 ---
13:01:56.719: Connect to 'smtp.frontier.com', timeout 3000 seconds.
13:02:17.810: 15: Peer connect failure

Pegasus Mail Info screen:

Pegasus Mail for Microsoft Windows
Copyright (C) 1992-2014, David Harris, all rights reserved
Electronic mail to support@pmail.gen.nz.

WinPMail version: Version 4.70 (Win32), Feb 27 2014, build ID 546
Language resources: Standard UK English resource set
Extension Manager version: 1.14
Operating mode: Standalone
User name and ID: Single-user mode, 0
Windows version: 6.1
Windows flag word: 0
WINPMAIL.EXE directory: C:\PMAIL\Programs
Home mailbox location: D:\MAIL
New mailbox location: D:\MAIL
TMP environment variable: C:\Users\Dilip\AppData\Local\Temp
TEMP environment variable: C:\Users\Dilip\AppData\Local\Temp
LAN-based SMTP support: N, N, N
NetWare MHS support: N, N, N
Built-in TCP/IP support: Enabled
  - WINSOCK version: WinSock 2.0
  - WINSOCK path: WSOCK32.DLL
Commandline: -A
Active -Z options: 32768
PMR variable: (None)
PML variable: (None)
MAI variable: (None)
NB variable: (None)
Autofiltering folders: 0 (0 active, 0 inactive)
Last new mail count: 4263
Message size soft limit: 0 bytes
Message size hard limit: 0 bytes
Attachment size soft limit: 0 bytes
Attachment size hard limit: 0 bytes
 

Enable Internet session logging (located at the bottom of the General tab in Tools > Internet options) then attempt a send and review the resulting log.  Read the help file about Internet session logging for info about where to find the log.  Do not post the log without obfuscating your login credentials.  They are difficult to identify in the log because of encoding but are easy to decode.  They follow the "Auth login" entry (4 lines in my logs).

The last few lines of the log should provide a clue as to what point in the process the failure is occurring.

Thanks. I see in my mail folder a new directory TCPLogs with one file, TCP-150316-1427-0.smtp. It doesn't have much, just the following,a fter I tried a mail send.

14:27:00.173: --- 16 Mar 2015, 14:27:00.173 ---
14:27:00.173: Connect to 'smtp.frontier.com', timeout 3000 seconds.
14:27:21.271: 15: Peer connect failure 

Sometimes it might help to just search the whole Internet for a solution, here's an example of what could be causing you issue.

There is no communication with smtp.frontier.com so my immediate thought was that your internet connection is down.  That is obviously not the case unless you are posting from a different machine.  You don't mention a problem with receiving so I assume that you are receiving mail ok.  The first troubleshooting step I would take is to insure no changes to anti-malware or firewall settings are blocking that port.  I would be especially suspicious of any product that monitors email and disable that monitoring or that product altogether during troubleshooting.

I might also create a new smtp host configuration using the settings found at the URL below.  Disable the old one and test with the new one.  Check the log if it fails.  If you see a failure that appears related to SSL then in the Security tab of the smtp host configuration reverse the setting called "Only use SSLv3...(enable if disabled & vice versa) and test again. 

https://frontier.com/helpcenter/internet/using-your-email/other-email/how-do-i-enable-ssl-encryption-in-my-email-program-

Yes, I can receive. But other weird things are happening - I can't ping, which just doesn't make sense. I just got off the phone with frontier tech. support and they are finding very slow line speeds, and sending a repair person, which hopefully will resolve the issue. I tried increasing the smtp timeout from 3000 to 5000 seconds, and email is still not sending.