Hi,

I had set up my mailcow yesterday, and it was working just fine. However, in the afternoon, it stopped receiving mail from any addresses over the internet. It still receives mail sent from its own postfix server, and my email client on my laptop is able to read that mail just fine, so I don’t think it’s a firewall issue. I am also able to send mail from mailcow server to my gmail without issue, so it seems that SMTP is configured correctly.

My mailcow is hosted on a Linode server, so if I am able to read my mail locally via IMAP, that means IMAP should be configured correctly. I also confirmed that Linode does not have any firewalls in place except to block port 25, which I do not need anyway.

The best I could figure to debug was to send an email from my gmail, and monitor the dovecot logs for any errors. However, Dovecot does not even log receiving a connection from GMail.

Since I am fairly confident it’s not a firewall issue, I am thinking the issue is DNS. So, I am wondering if anyone can see anything in my records which I cannot.

commands from my laptop (over the internet):

┌────adam@chi:~ 
└─[$ dig +short adamcooper.sh mx  
10 mail.adamcooper.sh.
┌────adam@chi:~ 
└─[$ dig +short mail.adamcooper.sh
45.79.50.168
┌────adam@chi:~ 
└─[$ dig +short adamcooper.sh txt
"v=spf1 mx ~all"
┌────adam@chi:~ 
└─[$ dig +short _dmarc.adamcooper.sh txt
"v=DMARC1; p=reject; rua=mailto:mailauth-reports@adamcooper.sh"
┌────adam@chi:~ 
└─[$ dig +short dkim._domainkey.adamcooper.sh txt
"v=DKIM1;k=rsa;t=s;s=email;p=MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEA0LCBD80etnyB67vFw11XIpxbQAcfrKu97t8RY+7bwEEYWH+Zjq5g7wHe4dMCxZ6j1lxwJOzlmb1c1JjKAhaM/Gb3/qTQwK8+5JPD3h5Gg1gQn57DMrJz0MQIpqiM67J1lOP6X9Qnu7G3HuymT0BKsyibZs23AQTtS3gVNyqOptbbW7TwBcv6MSG" "uZSUI+X0xeKUZ6ZDz8EGqGHskQb25IbsQdyeZjmSqe68Qi6XbylLKSa9Wl6ozbTP2fHsl9Qq7ZZ1H0yzhoNMDlM6Non7wb6/pU/jNBETSOQPJCB2v16Lhknrcha2lNfpK6IPVU7qyPrKJxqrjvDp+dlntA4IUfQIDAQAB"
┌────adam@chi:~ 
└─[$ nslookup 45.79.50.168
168.50.79.45.in-addr.arpa	name = mail.adamcooper.sh.

Authoritative answers can be found from:

┌────adam@chi:~ 
└─[$ nc -vz mail.adamcooper.sh 143
mail.adamcooper.sh [45.79.50.168] 143 (imap) open
┌────adam@chi:~ 
└─[$ nc -vz mail.adamcooper.sh 993
mail.adamcooper.sh [45.79.50.168] 993 (imaps) open

Commands from the Linode instance hosting my mail server:

root@localhost:~/Containers/mailcow# dig +short adamcooper.sh mx
10 mail.adamcooper.sh.
root@localhost:~/Containers/mailcow# dig +short mail.adamcooper.sh
45.79.50.168
root@localhost:~/Containers/mailcow# dig +short adamcooper.sh txt
"v=spf1 mx ~all"
root@localhost:~/Containers/mailcow# dig +short _dmarc.adamcooper.sh txt
"v=DMARC1; p=reject; rua=mailto:mailauth-reports@adamcooper.sh"
root@localhost:~/Containers/mailcow# dig +short dkim._domainkey.adamcooper.sh txt
"v=DKIM1;k=rsa;t=s;s=email;p=MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEA0LCBD80etnyB67vFw11XIpxbQAcfrKu97t8RY+7bwEEYWH+Zjq5g7wHe4dMCxZ6j1lxwJOzlmb1c1JjKAhaM/Gb3/qTQwK8+5JPD3h5Gg1gQn57DMrJz0MQIpqiM67J1lOP6X9Qnu7G3HuymT0BKsyibZs23AQTtS3gVNyqOptbbW7TwBcv6MSG" "uZSUI+X0xeKUZ6ZDz8EGqGHskQb25IbsQdyeZjmSqe68Qi6XbylLKSa9Wl6ozbTP2fHsl9Qq7ZZ1H0yzhoNMDlM6Non7wb6/pU/jNBETSOQPJCB2v16Lhknrcha2lNfpK6IPVU7qyPrKJxqrjvDp+dlntA4IUfQIDAQAB"
root@localhost:~/Containers/mailcow# nslookup 45.79.50.168
168.50.79.45.in-addr.arpa	name = mail.adamcooper.sh.

Authoritative answers can be found from:

root@localhost:~/Containers/mailcow# nc -vz mail.adamcooper.sh 143
mail.adamcooper.sh [45.79.50.168] 143 (imap2) open
root@localhost:~/Containers/mailcow# nc -vz mail.adamcooper.sh 993
mail.adamcooper.sh [45.79.50.168] 993 (imaps) open
root@localhost:~/Containers/mailcow# source .env
root@localhost:~/Containers/mailcow# echo $MAILCOW_HOSTNAME
mail.adamcooper.sh

If nobody sees any issue, any steps on how to debug? I tried desperately to find a tool like MXToolbox but for IMAP, but it doesn’t seem any exist.

Also, if you want any information about my config, please ask!

Thank you!
Adam