Can't connect to one specific mail server in one specific network, other providers work.

Hello community, at my place of work no one can send or receive mail anmore using Thunderbird. The problem suddenly appeared last monday. No changes regarding the network or settings in Thunderbird happened prior to this. Here's what I tried so far and things I can rule out: * same problem appears on all devices (desktop and laptop PCs) in our office * our work mail server is online and working, I can access everything using the webmail-interface in the office network * new installation of Thunderbird without any profiles and fresh account confguration doesn't solve the problem * I can connect to our mail provider and send and receive mail when using my home network or my personal phone hotspot * I can connect to my private mail provider using Thunderbird while in the office network * troubleshooting mode doesn't solve the issue * renewing the internet connection on our router temporarily/once allowed some devices to receive mail * pinging the mail server (mailserver.[''workdomain''].de, no specific port) via command line was successful while Thunderbird was unable to connect to the mail accounts IMAP-Log returns the following error codes: * D/IMAP URL failed with code 0x804b000e * D/IMAP URL failed with code 0x804b001e I would be glad if somebody could help me out. If you need any more details I'll provide them. Thanks in advance!