[Users] Basic SMTP authentication issue

[Will Meister]

Hello guys, I'm a very new user of Claws and suspect that this is one
of those queries that comes up often -- sorry for being boring.

I installed Claws because a client asked me to access their POPmail. They
gave me my username and password:

will at clientdomain.com
random_st8ff

incoming and outgoing servers, both:

mail.clientisp.com
mail.clientisp.com

(I'm guessing POP/SMTP)

I can download mail reliably. Sending mail usually gets an authentication
error. I  tried the obvious variants as SMTP authentication /PLAIN / LOGIN;
here's a log from the failed send:

* Account 'will at ziggytec.com': Connecting to SMTP server:
mail.blacknight.com:25...
[21:44:21] SMTP< 220 mail.blacknight.com ESMTP
[21:44:21] ESMTP> EHLO niftynetbook
[21:44:21] ESMTP< 250-mail.blacknight.com
*** Error occurred while sending the message.

I suspect that this is going to be something small and subtle between the
program and this particular ISP's setup, which appears idiosyncratic. TIA
for any help.

WM.
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