GMail POP3 authentication fails randomly

tesirm99

Hello, I have recently configured Mailcow-dockerized as a mail server with my own domain. After setting everything up (my mailbox, opening the needed ports, etc.) I configured my Gmail account to be able to receive mails from my mailcow mailbox there using POP3S, but I am having random authentication issues. Here is a screenshot of Gmail’s POP3 history:

I have checked Dovecot’s logs and this is the error I am getting:
Jun 3 08:11:36 8f7735e4bee1 dovecot: auth-worker(19415): HTTP request failed with closed for user mymailbox@mydomain.com Jun 3 08:11:36 8f7735e4bee1 dovecot: auth-worker(19415): conn unix:auth-worker (pid=136,uid=401): auth-worker<3>: lua(mymailbox@mydomain.com,2a00:1450:4864:24::,<CV7FwKQ255MqABRQSGQAJAAAAAAAAAAA>): Password mismatch (SHA1 of given password: blablabla) Jun 3 08:11:38 8f7735e4bee1 dovecot: pop3-login: Disconnected: Connection closed (auth failed, 1 attempts in 2 secs): user=<mymailbox@mydomain.com>, method=PLAIN, rip=2a00:1450:4864:24::, lip=fd4d:6169:6c63:6f77::a, TLS: Connection closed, TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits)

I have also created and configured an App password with all the protocols and updated it in my Gmail.

As I am no expert in this field, I am using the default configuration for everything except the domain and reverse proxy (I am using Nginx and followed the documentation guide for that case).

I have looked for posts with similar issues but found none. Can anybody help me?

Thanks!

tesirm99

I have narrowed the issue to the passwd-verify.lua script used for auth when the cache fails. It stops working randomly, I get a closed connection for the http request it makes to the nginx server (and php-fpm). I have also checked both php-fpm and nginx logs and all the requests made are successful (200 OK).
This issue happens both for POP3 auth and for SMTP auth with Gmail. I don’t have 2FA enabled and I have tried using password and setting up application passwords with POP3 and SMTP permissions, but it still fails randomly.

Does anyone have any ideas on what could be the issue?

leonidas-o

I’m facing the same issue, my Mac OS Mail App works most of the time, but then randomly I see the connection issue icon appearing, because fail2ban bans my IP Address. Going over VPN (whitelisted IP), when I check the Mailcow netfilter logs, I see something like:

XXX.XXX.XXX.XXX matched rule id 6 (auth-worker(25235): conn unix:auth-worker (pid=129,uid=401): auth-worker<37>: lua(my-user@my-domain.com,XXX.XXX.XXX.XXX,<foo...>): Password mismatch (SHA1 of given password: abc...))

So out of nowhere the password starts to fail, which doesn’t make sense, as most of the time it simply works.
@tesirm99 did you found a solution?