What can lose access to your mail server?

Good afternoon. There are 2 rooms, Internet from 1 provider, but 2 different router and 2 dynamic ip (all devices in room 2 and connected to the router 2 errors are identical).

In 1 room, all is stable, in the second mail access (send message or even log into the user account) periodically absent, the Internet works flawlessly. The cause of the outage was not clear, he sometimes resumes. For example, in PT care - did not work in the PN - come- all-day, in W open until 9 am and is disabled until the router was not reconnected (helped 20 min), a software reboot of the router does not help. Client - Thunderbird, when not working, tried to download other clients didn't help. Through the web-mail interface does not go. Router settings dropped, the provider says that they do that create this problem are unable to do. Tried the client to change ports, protection methods (SSL/TLS) - nothing helps. The mail server is pinging, even when running mail, so it's not him, the people responsible for the server say that the problem we do not know what MB problem.
On this router 18 PCs + phones, MFP. On the phone is the client, switch to wi-fi with 1 rooms or 4g - works.
Error, by the way: "Error sending the message. The MB message is not sent, since the timeout of the connection to the outgoing mail Server (SMTP) "domain-mail" has expired. Try again"
The logs, at 11:35 was not working at 11:40 works like nothing normal5e26d1ba16557710932448.png
Solution to see only 1 - to change the router, but no spare and not the fact that will help, and buy just that

upd1: the provider said that with this problem you need to contact the mail server and tell them that we have 2 gray IP behind a NAT. 2 is a view of the grey room 1 and room 2.
upd2: hooked other router, while watching his work
April 4th 20 at 13:09
1 answer
April 4th 20 at 13:11
Of tasks it is unclear how all sconfigured,
1. Both rooms have a shared network?
2. In the screenshot DHCP logs, if claim 1 is true, then you have 2 DHCP in one network?

The phrase "(in the room containing all computers that are connected to the router, the errors are all identical)." I read several times, did not understand.
1. No
2. P1 is not true)
Sorry, a little confused. There is a view that in both "rooms" on the routers are connected through 5 and 18 PC, respectively, and errors of all devices connected to the room 2 are identical. - alysso commented on April 4th 20 at 13:14
@alysso, router model write. Something I have a suspicion... what is SOHO-soap dish for 3 to 4 thousand rubles, in this case, nothing surprising that with 18 PCs N smartphones such glitches. Would not be surprised the same effect with 10 PCs, and even without smartphones. Routers this class is designed for home use 4..5 PCs and many smartphones - reasonable maximum, then the router cannot cope with the load and effects can be different. - andres96 commented on April 4th 20 at 13:17
@alysso, well, first this is not an error, this is an informational message.
in the second mail access

mail is where? errors mail program give. - Reyna_Nitzsche47 commented on April 4th 20 at 13:20
@andres96, tp-link TL-WR840N router for "small and home offices", as written in the manufacturer's website. I would have bought something more expensive, but is unlikely to receive a permit, and if the problem will remain, yourself, must know what can be - alysso commented on April 4th 20 at 13:23
@Reyna_Nitzsche47server in Kiev, customers in all regions of the country. 5e27e66c7a6a5310928389.png - alysso commented on April 4th 20 at 13:26
@andres96, revered, it would be interesting something like that to do, do we want to go. On windows have done PC to the router, but the problem was slightly different. Do you think that such a solution will indeed be better for a 20 PC than the conditional router for$ 50, despite the fact that the router will still be needed for wi-fi? - alysso commented on April 4th 20 at 13:29
@alysso, it has some kind of pattern? mean error, well, that is 100% possible to play or is it randomly happening? Sure that mail server is available in the other room? Occurs only in 1 room at odnogo person or all at once, everything falls off?
Just if the Internet continues to work, and mail is not, how would the router do with it?
Ask yourself all these questions, consider before you change routers at random, I'm from the services of vehicle maintenance is also run when you tell them, the noise in the clutch, he neglyadya - grip replacement... - Reyna_Nitzsche47 commented on April 4th 20 at 13:32
@Reyna_Nitzsche47, the fact of the matter is that all of these questions I already answered in the thread, but for myself especially. Therefore I appeal to the people who have knowledge, at least I think so, on some level higher than me. The pattern if there is, I did not find it; play it does not work; I am sure, just connect to another wi-fi and everything is OK; all at once, on all devices at once, to all clients immediately. I don't know what to do with it, err on the router, because the provider says he brought the server says that it is not being room 1 with router 1 says, we have all the rules, the only thing that remains is the router 2 - alysso commented on April 4th 20 at 13:35
@andres96, even the replacement router didn't help, however, on the same home.
pings go to the web interface of the standard "unable to access site" - alysso commented on April 4th 20 at 13:38
to another wi-fi and everything is OK

awesome nuance -) i.e. you have 15 cars sitting on wifi? then it radically changes things. Here only will help to apothica on good equipment, or make a wired network. - Reyna_Nitzsche47 commented on April 4th 20 at 13:41
@Reyna_Nitzsche47, no, I just phone to connect to another wi-fi, since on our is not working, the computers connected through switch - alysso commented on April 4th 20 at 13:44
@andres96in the web interface through VPN comes - alysso commented on April 4th 20 at 13:47
in the web interface through VPN comes
I would think that some kind of lock, if the server and clients were in different countries... Although it can be lock from the server side, something like fail2ban. - andres96 commented on April 4th 20 at 13:50
@andres96, the provider said yesterday to upload information that we have gray IP behind a NAT. Some idea what it is, I wonder could this be the problem. Because 1 the network is working normally, it can be assumed that at some point the 1 server IP address enters too much data and the server "asks" to calm down a little by the ban for some time - alysso commented on April 4th 20 at 13:53
@alysso, Yes, this is possible. - andres96 commented on April 4th 20 at 13:56
@andres96and solution please? Understand that you can divide your network into subnets, in this case to pay more; to ask not to ban our ip, but it is gray like the option to buy white and ask him not to ban. Can in this case help to replace the router on the same$ 300, a little doubt, but for a more stable job would be nice.
If you take Mikrotik conditional for 50$(MikroTik 951Ui-2HnD - the first thing that caught) whether it is better to celebrate in this network?
Sorry for so many questions, just except Google no one to ask, and he's not very responsive for specific tasks :) - alysso commented on April 4th 20 at 13:59
One more thing, we recently switched from POP3 to IMAP, maybe even this was the reason - alysso commented on April 4th 20 at 14:02
@alysso, sending is still SMTP, so the client Protocol here neprichem. Yes, there is more similar to the block count of the sessions on the server. Correctly told you above, maybe the admin of the mail server peredel and limited number of simultaneous connections from the IP. Maybe someone changed the password, and he tries pounding on the server and have the server block the address for that. In any case, you need to contact the owner of the server and mail together to solve the problem. - Reyna_Nitzsche47 commented on April 4th 20 at 14:05
@alysso, I agree with @Reyna_Nitzsche47.
And what about the 951 th Mikrotik - not worth it. This is also a very weak router. For home is good, Yes. Its advantage is very feature-rich functionality, and that the regularly published updates of the firmware. But the performance is low.
And in the case of locks for mail server replacement router will not help. - andres96 commented on April 4th 20 at 14:08
@Reyna_Nitzsche47, Yes, most likely it was. Tried when mail worked 50 times to enter incorrect data in the web interface- got banned. Now walked on all computers, deleted all unnecessary - alysso commented on April 4th 20 at 14:11
@alysso, well, fine. More money on the router with a saved -) - Reyna_Nitzsche47 commented on April 4th 20 at 14:14
@Reyna_Nitzsche47, I hope will never happen again, an incredible relief, after a week of odds) thanks for the assistance :) - alysso commented on April 4th 20 at 14:17

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