My wife just switched to a lower cost internet hosting service. Her web sites work fine, but email has been mostly kaput. The email set up is pretty a pretty standard IMAP/SMTP with authentication.
I have an email account on her domain. Setting up on an Outlook client on my desktop PC failed. Setting up on an Outlook client on my Android phone also failed. I didn’t have time to troubleshoot at that point and a few days later, my wife stated the emails were now working. Sure enough, I was able to configure and connect Outlook on both my desktop and phone. Test emails were sent and received and all was well… for one day. A few days later, it again worked for a day before failing.
At first, I just cursed the new provider as cheap an incompetent, and then started I troubleshooting. Pings from my desktop to the IMAP timed out. Using an external ping web site, pings to the server responded quickly. I switched off the wifi on my phone so it was using the data connection for my cell provider which is a different company that supplies the internet to our home. Outlook happily connected to the servers for sending and receiving test messages. I turned the wifi back on, and I no longer could connect to the servers.
The host name does resolve. I should have checked the IP address of the internal ping and the external ping to see if they were the same. Unfortunately, I cannot do this now because the email has decided to start working again. I’ll have to keep that in mind of the email stops working tomorrow as has happened the past couple of times it worked.
Does the web version for email at the provider work (you stated that websites work fine but not sure if you mean web email)? Did you try a different email client other than Outlook? I have had to switch from different email clients because they just stopped working (I was using a Eudora Clone I think it was called Postbox- I really miss Eudora) and it worked fine for years and than it started having problems and even the Dev couldn’t help. I ended switching to Outlook for home needs at that point. Though Outlook has problems sometimes too for no reason that I can tell.
She moved the domain to a new host, so I meant her web site was working. I did not try a different client. The fact that I was unable to ping the mail host means that it isn’t a client problem. I even opened up a telnet session and could not make a connection via telnet.
I think this or DNS caching might be it. If in doubt reboot, and so I did reboot the cable modem. I checked for a connection to the server after it finished rebooting. No connection, but the mail host became reachable a little later. I wonder if the reboot initiated some sort of cache clearing that took a while to finish. The thing that I find really odd about this is that the problem has been intermittent which doesn’t really fit well with an old cache.
Routers along the many paths start caching at different times, so it might still be that. Although, a quick googling told me TTL values are not days-long anymore, so maybe not.
Routers generally don’t care DNS records unless they are serving as DNS servers for the local network, but if the problem is intermittent over several days, it does sound like a DNS record got stuck somewhere, and when servers or clients try to refresh their cache, they sometime get the wrong answer.
When we say email doesn’t work, does that mean sending or receiving?
Is there an error or bounce message?
When you switched the web host, did you change the ns servers for the domain, or just pointed them to the new web and email servers?
Is there a web interface for the mail, and if so does that work correctly?
I should clarify that after troubleshooting, email sending and receiving by the host provider is working. What I am not able to do consistently is to connect to the mail server for sending or receiving from a client within my home network. I can connect when I am on a network outside my home network. The inbound email is via IMAP with authentication, and the outbound email is via SMTP with authentication. I have used telnet to try and connect from my home network and failed to connect to the server, and then immediately used a remote online telnet client and was able to connect.
When the connection fails, is the server name resolving to a wrong IP? Does the telnet connection work when you try to connect directly to the IP?
If it is a DNS issue, the next step is tracking down what IP your computers are checking to resolve the server name, and what is the DNS server they are checking and so on. As a workaround you can set your email client to connect to an IP address instead of a DNS name.
