Mail to one address fails from server, but ok from other email servers

[MCubitt]

(ABC used for sample)
I receive:
14/11/2003 15:16:43 Router: No messages transferred to ABC.CO.UK (host mailgate02.ABC.CO.UK) via SMTP: SMTP Protocol Returned a Transient Error
14/11/2003 15:16:43 Router: No messages transferred to ABC.CO.UK (host mailgate01.ABC.CO.UK) via SMTP: SMTP Protocol Returned a Transient Error
14/11/2003 15:16:47 Router: Failed to connect to SMTP host ABC.CO.UK because SMTP Protocol Returned a Transient Error


Sending an email from our Lotus Notes does this. From my personal (webmail) account, no problem.

I want to discover where the problem is, any suggestions which path to trace?

I understand the problem can be
1) leaving us - Notes
2) leaving us - Firewall
3) our ISP
4) their ISP
5) arriving to them - Firewall
6) arriving to them - Email server

plus other areas, I guess.

This problem has been going on for a few months so is not isolated. Other emails to other hosts are sending correctly.

I have tried various @ABC.co.uk

Any ideas, please?

 

[MCubitt]

Not sure if this is partly, wholly or totally-un relevant:

H:\>ping mailgate02.ABC.CO.UK

Pinging mailgate02.ABC.CO.UK [162.19.26.213] with 2 bytes of data:

Reply from 19.1.4.10: Destination host unreachable.
Reply from 19.1.4.10: Destination host unreachable.
Reply from 19.1.4.10: Destination host unreachable.
Reply from 19.1.4.10: Destination host unreachable.

Ping statistics for 162.19.26.213:
Packets: Sent = 4, Received = 4, Lost = 0 (0% los
Approximate round trip times in milli-seconds:
Minimum = 0ms, Maximum = 0ms, Average = 0ms

Same with mailgate01

 

[HiAll]

Check your server whether it can resolve the mx record of mailgate02.ABC.CO.UK first.
Then, you should try whether you can send a mail to mailgate02.ABC.CO.UK with telnet (use port 25).
Also, I don't think you can ping their server as their firewall block it always.