[CentOS] Mail has quit working

Mon Aug 27 11:57:41 UTC 2018
Richard <lists-centos at listmail.innovate.net>


> Date: Monday, August 27, 2018 07:42:48 -0400
> From: TE Dukes <tdukes at palmettoshopper.com>
> 
>> From: CentOS [mailto:centos-bounces at centos.org] On Behalf Of
>> Richard Sent: Monday, August 27, 2018 7:29 AM
>
>> 
>> Since the localhost4 approach worked, commend out the ipv6
>> localhost entries in your /etc/hosts file, then try:
>> 
> IP6 is commented out
> 
>>     dig @localhost localhost a
> 
> That works
>> 
>> again. If that works try:
>> 
>>     telnet localhost 143
> 
> This also works
>> 
>> once again. If those work, it would seem that your ipv6 is messed
>> up and your system is trying it first and not falling back to ipv4.
>> 
>> Regarding your nameserver list in /etc/resolv.conf. If you have a
>> working 127.0.0.1 nameserver you generally don't include external
>> nameservers in that list. So, if non-ipv6 things seem to work, I'd
>> remove the two non-127 nameservers from that list.
>> 
> Removed the two nameservers. Still can't access mail. Getting
> connection to storage server failed on the roundcube login page.
>> 

That you can now successfully get to "localhost" is good progress.
Seems you want to stay away from ipv6 networking issues unless/until
you resolve whatever that issue is.

Roundcube is, potentially, a totally separate issue. I don't use it,
so can only suggest minimal debugging ideas.

What is the hostname that you use to get to your roundcube instance?
Can you resolve that:

   dig <hostname> a

If you get an answer, is the ipnumber correct?

Note, if the hostname for your roundcube instance is one of the ipv6
entries in your /etc/hosts file, I'd remove that - and either put in
an ipv4 entry or put an entry for it in your dns.