Symptoms

Mail delivery fails with error 554:

    55CE7280131: to=<test@domain.tld>, relay=plesk_virtual, delay=1.7, delays=0.17/0.01/0/1.5, dsn=2.0.0, status=sent (delivered via plesk_virtual service)
    55CE7280131: removed
    0572C2801E1: uid=30 from=<qwe@plesk.tld>
    0572C2801E1: message-id=<6AD1BED0ECFB2E4FA52CC9B923AE4ED6A50F7157@doma2.tld>
    0572C2801E1: from=<qwe@plesk.tld>>, size=3826, nrcpt=1 (queue active)
    0572C2801E1: host mx03.domain.tld refused to talk to me: 554 IP=IP_ADDRESS - A problem occurred. (Ask your postmaster for help or to contact tosa@rx.domain.tld to clarify.) (BL)

Cause

Error code 554 means IP-Blocking, remote mail server are not currently accepting e-mails from your IP address used by your clients. This IP blocking may be due to a previously observed unusual volume of e-mails at the IP address concerned.

Resolution

Check mail connection using telnet:

    # telnet mx03.domain.tld 25
    Trying mx03.domain.tld....
    Connected to mx03.domain.tld.
    Escape character is '^]'.
    554 IP=IP_ADDRESS - A problem occurred. (Ask your postmaster for help or to contact tosa@rx.domain.tld to clarify.) (BL)
    Connection closed by foreign host.

Contact remote mailserver administrator