I doubt that the number of accounts is the problem.

The only thing that comes to mind is that an av or anti-malware program might be interfering with Pmail.

In the long term you should exclude Pmail from such scanning, but initially turn them off to check whether they are the issue.

Sometimes, suddenly, all my POP3 accounts simply disappear from my list of POP3 hosts (Tools/Internet Options/Receiving (POP3))

Other times only some of them are gone.

I have to Add them back which is becoming a pain.

The same sometimes happens with my SMTP accounts. Then I cannot send emails.

Help! Any ideas? 

I don't know why you are losing them. You can at least same some work by making copies of the definition files.

These can be found in your mailbox. File names begin with SMT or POP and both have the extension PND. They can be viewed with Notepad.

When they do disappear  from settings are they also missing from the mailbox?

I believe they are there - never checked.

I can add them back from the Available POP3 definitions list and the SMTP list.

You have a good suggestion, though, and I will follow up on that. 

Not terrible, but frustrating, and then some accounts pile up if I miss it.

Thanks for your reply. 

If you are not having to re-define them the files are there.

Which version of Pmail and what OS?

Any recent changes to either?

sorry for the delay-

v4.7

Windows 7 Home Premium

No changes in a long time.

I forwarded several accounts to consolidate, and now have just 10 POP3 accounts

Is too many accounts a problem?

Anyway, no big deal. Love the program too much to complain