mail server not acceoting P/W error 451

I've talked to the service provider and he is convinced that there is some glitch in either c-panel's or the 3rd party's webmail softwares/services that is causing this problem and I don't know enough about the particulars to know better- one way or the other.

Prior to today, I didn't receive email in my Webmail, for approx 36 hrs, other than some tests I sent out from my IP email. Than this morning, I received Sat, Sun and Mon AM mail all at once. Now I've got a client server problem. I am able to open up webmail ie(SquirrelMail) but the P/W is not being accepted by the server from my email client and the settings have not been changed or altered from when the client-server were working properly, together. It's pop and I'm using mail.mydomain.com for the server address. Because cpanel sets the default email accounts w/ the acct. user names, I have created secondary accts for the default/catch all email addresses. ie "info@" is my default catch-all address and the"AcctUserName@" that cpanel assigns is not used. The complete address ie info@mydomain.com has been the user name on the eml client side, and this is what has worked in the past but, not now. Additionally, I set my email to be forwarded to my IP email address and it is not being forwarded to my client. I haven't checked the IP server yet but will after finishing this post.

The only additional details that I can provide are: 1) There was a recent server Swap. (My sites are up) 2) I received this error in my return email: (reason: 451 Could not complete sender verify callout) 3) I use the MacOS email client.

I'd appreciate any ideas, advice or tips on this.

 

Thank you. I sent this info along to the server host. Is there anything I can do through WHM or is this something for the admin, (other than server name resolving)? FWIW I ran the mail troubleshooter on the domain mail accts in question and no routing errors or probs showed up.

 

This is Maddening

Here is the answer I received from the server admin:

He did a swap over the weekend and it can't be a coincidence that my problems started at the same time. I don't know enough about the process to have the overview that I need to pinpoint a solution, so, I guess I'm destined to spray out raw info and possible clues, as I run across them.

A reminder-
The Problem: my server is not recognizing the password that is being sent by client. The password is correct because I can access the webmail acct with it.

1)When I go to mail.[mydomain].com the page resolves to a c-panel message:

2) The mail folder is showing that it was either, (I'm not sure which) created on, or last accessed on 10/2 which coincides w/ the beginning of my probs and the server swap. I wasn't there- The 1st time I FTPd to the domain was today.
3) I have changed my user name from info@[mydomain].com to info+[mydomain].com w/o success
4) This is a shot in the darl and probably immaterial but... I'm not certain, but it seems that there are some new folders w/ the domain that weren't there before. I could be wrong because I'm so accustomed to going straight to public_html that I rarely see all of the site files. I don't recall seeing cpanel3-skel or etc before but that dosen't mean they weren't there. The mail folder is showing that it was either created on or last accessed on 10/2 which coincides w/ the beginning of my probs.

 

The server gets swapped, my websites resolve, I key in new P/Ws through my site management software, cpanel, I can access Webmail through the cpanel interface, but the the mail server is rejecting the P/W from my client: "POP server “mail.h[my domain].com” rejected the password for user info+[mydomain].com" (as well as, info@[mydomain].com.

There has to be a file, somewhere in there w/ the site files that got misplaced/tweaked or when the swap took place a new file got "auto-placed" in w/ my site folders that may be overiding old commands or the settings got changed or something! I am totally dependent upon cpanel to help me manage my websites. I don't know where else to turn to. I'm willing to do the work and research, I just need someone to point me in a direction. I receive 100s of emails a day and it's been 5 days of the server denying my client access. I did nothing out of the ordinary to cause this problem- it just started happenning out of the blue.

Should I change my master accts DNS, ie the one that I run WHM w/, download my sites and rebuild my package/ acct list? I have a few medium sized sites and about 50 small sites that I'll need to redo- plus Dreamweaver server settings, FTP settings etc to deal with.

Any input or a link to a forum that focuses on servers, mail protocol etc. would be greatly appreciated. Thank you.

 

Am I in the Right Place?

Did I lay out the problem clearly, enough?

Did I, mistkenly, say something and unintentionally convey a subtext in my request for help that has caused others to cop a passive-aggressive attitude and use a non-response demonstration of their displeasure w/ me?

Is the problem a singularity, ie the problem has never happenned before and may, never happen again?

If not, is there anyone here w/ experience or who is in the know at the forum who could offer some trobleshooting suggestions or, perhaps, a possible solution?

Am I expecting too much from a support forum? I have been around here for about 3 days pleading for help and can see that, at this writing, there have been over 50 views.

Am I on the wrong forum board or did I miss or overlook a FAQ that provides a solution to my problem? God knows, I have searched.

Is this not a cpanel problem or something that can be solved in cpanel, at all, in which case, I have been wasting my time, I apologize for wasting your bandwidth and I will need to re-evalute my relationship w/ dedicated servers based on my abilities, aptitude or lack thereof.

Thank you for taking the time to read this and for allowing me to share some of my thought processes w/ you.

I'll check back in later tonight and, once, again in the morning, after which I will not bother you any further.

 

This Really Sucks!!