So you work for the NSA? Seriously you have redacted so much when you have included is meaningless.

Thank you. I just quoted the error message I get when the incoming mail is not coming through. This error message literally says 'mail server <name of the pop server> responded: n-Path: <email address of sender>. I thought this info be an adequate description of the problem, and that the actual name of the pop server and email address would not be material to the problem/solution, as is my actual email address where the incoming mail query produces the error message . Am I wrong here?

Outgoing mail is working fine, incoming mail is not. On my i-pad the same email address I use gives no problem. Only when using Thunderbird on my desktop it jams, producing the error message.

It is the incoming server that I am looking for, and the additional information that the email address mentioned is yours. With the email server I can yest the server and check settings that should work. Without it I am flying blind.

OK Matt, I'm obviously too simple minded in this matter. The incoming server is: pop.hetnet.nl The error message reads in full: mail server pop.hetnet.nl responded: n-Path:<XXXXXXXX@163.com> [I presume the latter is sender's mail address causing the error] My email account in Thunderbird: XXXXXXX@hetnet.nl Will this info do? Thanks for your perusal

hetnet.nl does have some issues. But nothing that should cause he error.

The sender is not listed in any email blocklists as a source of spam that I can see.

I did find a reference to McAfee anti virus in one source. Do you use that? This does appear to be a mail server fault. Have you contacted your mail service provider?.

I have edited your last post to remove some informatio9n that is not really required.

I don't use McAfee, not installed. I use VIPRE antivirus. I did not contact my provider yet, as the jam of incoming mail on this email-acount only occurs using Thunderbird.

I just did a check how Windows Live Mail would handle incoming mails for this account. The incoming mails are not blocked, they appear in my INBOX. But I do receive window-notice of "time-out occurred during communication with server'. Server error 0x800CCC90. Server responds Return-Path <xxxxx@163.com> (same sender as in Thunderbird notice) Server: 'pop.hetnet.nl'. Windows Live Mail-error-id: 0x800CCC19. Protocol: POP3." So besides the notice the mails are received in Windows Live Mail. However I prefer to use all my accounts in Thunderbird, and would like to have this problem solved.

Does this shed new light on where the problem lies? Could the outgoing server of senderé account have something to do with it?

You use two different mail clients and both give you errors. pretty obvious where the problem lies. As I said it is a server error. Quite possibly a corrupted inbox. Contact your mail provider.

Nor that what happens or not in web mail is totally irrelevant.

Ok, provider solved the problem. Thanks your help Matt