Exim wont start using systemctl but it will via exim debug

I have a problem where Exim4 will not start/restart/reload... nothing works via /etc/init.d/exim4 nor systemctl start exim4... Both produce no output on the console - the start procedure just hangs indefinitely. However when I start in debug via exim -bd -d, exim loads and no obvious errors on the output.

Systemctl & init.d scrip produce no logging as to why the start script fails. I am also a bit confused why it just hangs... Whats even more weird is that after about 20 minutes of failed attempts at starting service, the system 'somehow' just brings back Exim and status starts to report service as (active running)

Status output show

root@mail:/usr# systemctl status exim4
● exim4.service - LSB: exim Mail Transport Agent
     Loaded: loaded (/etc/init.d/exim4; generated)
     Active: inactive (dead) since Wed 2023-03-15 15:49:00 CET; 18min ago
       Docs: man:systemd-sysv-generator(8)

Mar 15 15:48:35 mail systemd[1]: Starting LSB: exim Mail Transport Agent...
Mar 15 15:48:36 mail exim4[8814]: Starting MTA: exim4.
Mar 15 15:48:36 mail systemd[1]: Started LSB: exim Mail Transport Agent.
Mar 15 15:49:00 mail systemd[1]: Stopping LSB: exim Mail Transport Agent...
Mar 15 15:49:00 mail exim4[9454]: Stopping MTA: exim4_listener.
Mar 15 15:49:00 mail systemd[1]: exim4.service: Succeeded.
Mar 15 15:49:00 mail systemd[1]: Stopped LSB: exim Mail Transport Agent.

Any insight on how to debug this would be greatly appreciated as I do not want to wait for a prolonged time when restarting the service.

[pid 30258] recvmsg(3, {msg_name=NULL, msg_namelen=0, msg_iov=[{iov_base="l\4\1\0013\3\0\0\22\0\0\0\266\0\0\0\1\1o\0.\0\0\0", iov_len=24}], msg_iovlen=1, msg_controllen=0, msg_flags=MSG_CMSG_CLOEXEC}, MSG_DONTWAIT|MSG_CMSG_CLOEXEC) = 24
[pid 30258] recvmsg(3, {msg_name=NULL, msg_namelen=0, msg_iov=[{iov_base="/org/freedesktop/systemd1/unit/m"..., iov_len=995}], msg_iovlen=1, msg_controllen=0, msg_flags=MSG_CMSG_CLOEXEC}, MSG_DONTWAIT|MSG_CMSG_CLOEXEC) = 995
[pid 30258] recvmsg(3, {msg_name=NULL, msg_namelen=0, msg_iov=[{iov_base="l\4\1\1\254\3\0\0\23\0\0\0\266\0\0\0\1\1o\0.\0\0\0", iov_len=24}], msg_iovlen=1, msg_controllen=0, msg_flags=MSG_CMSG_CLOEXEC}, MSG_DONTWAIT|MSG_CMSG_CLOEXEC) = 24
[pid 30258] recvmsg(3, {msg_name=NULL, msg_namelen=0, msg_iov=[{iov_base="/org/freedesktop/systemd1/unit/m"..., iov_len=1116}], msg_iovlen=1, msg_controllen=0, msg_flags=MSG_CMSG_CLOEXEC}, MSG_DONTWAIT|MSG_CMSG_CLOEXEC) = 1116
[pid 30258] recvmsg(3, {msg_namelen=0}, MSG_DONTWAIT|MSG_CMSG_CLOEXEC) = -1 EAGAIN (Resource temporarily unavailable)
[pid 30258] ppoll([{fd=3, events=POLLIN}], 1, NULL, NULL, 8

Ok so I actually figured out what was going on but I am absolutely not sure how is this even related...

So what it was, my mysql-community-server was totally corrupted (Exim4 does not use MySQL for any of its purposes...), but anyhow. After completely reinstalling MySQL, Exim4 started to behave normally - that is, start, stop, and reload worked without any prolonged delays.

Try rebuilding any database that Exim uses.

There's several ways Exim can use, e.g. MySQL: routing/configuration, virtual domains/users, whitelisting/blacklisting, and logging/statistics.

https://www.exim.org/exim-html-current/doc/html/spec_html/ch-file_and_database_lookups.html

I know on the servers I've seen, eximstats used MySQL. Users would often fill their drives or overload their servers in different ways, and eximstats and MySQL often broke down hinting at their problems.