Problem on mail-server on new location

[eko_taas]

My ISPConfog 3.0.3.3 was working just fine on earlier location (after great help of you guys), but now on new location & ISP and router (Buffalo ADSL) I have ended up trouble on mail-server.
- All ISPConfig servicies green / running w/o problems (as I use them)
- Fetchmail OK (from yyyy@test.com to zzzz@example.com)
- Sending mail with roundcube zzzz@example.com => zzzz@example.com OK
- Sending mail with roundcube zzzz@example.com => yyy@test.com OK
- receiving from other email to zzzz@example.com gives trouble (copied from email delayed alarm)

<zzzz@example.com>: connect to example.com[83.zzz.yyy.zz]:25: Connection timed out

As I have 2 routers in my system, I have made server1 as DMZ in Buffalo. Also portscan shows that needed ports on example.com are open (21, 22,) 25 (, 53 etc.). Also individual port-forward sis not change situation better.

What to check next - thanks for advice already now.

[eko_taas]

Seems that after more detailö check, on ISP-side port 25 is closed (all others open). Last time I scanned only locally

I have contacted them and ask for the same (as all should be open).