Windows 7: Server error 554

Am suddenly unable to send out emails, help

What service, what program, tried contacting ISP in case of ISP serviced mails? Please provide more information so that we can actually help you!!?

Sorry, it was a shock ! Am using Win Live Mail with ENTADSL, the message reads :-

Server Error: 554
Server Response: 554 5.7.1 <yottiejohn@googlemail.com>: Relay access denied
Server: 'smtp.entadsl.com'
Windows Live Mail Error ID: 0x800CCC79
Protocol: SMTP
Port: 25
Secure(SSL): No

So you're using the Windows Live Mail program to retrieve emails from your ISP's service? Try accessing the mail service directly from the website just to make sure the server is working normally. TBH it seems like a server side issue and nothing you can do about it but wait for it to be rectified or call them.

OK have emailed Enta from another source, no reply yet. This email set-up was transferred from my old XP machine and has worked OK up to now, it occurred to me to try it out on my old machine, and it works! Mail can be sent out and received normally.
I am away for brief periods and use a 3 dongle on the offending machine, I have never been able to send out messages from Win Live when using the dongle but have learnt to live with it. All is well again once I return home and plug into Enta (except for now).
Have checked my settings which seem OK. Have tried to access my account through Webmail but am unable to do so, I could previously. Thank heaven I have other email facilities to fall back upon.

Which program did you use to access this account on XP?

Honestly, WLM client is nothing but trouble ... consider using Thunderbird if it's alright with you.

Hope I'm no being thick here but do I understand it that there is nothing amiss with Enta, the problem being with Windows Live Mail ?
I just naturally used this when being confronted with Win 7 on the new lap-top, looks as though I was a bit hasty.

Windows Live Mail is a useless program, it corrupted on us after several months. Try Mozilla Thunderbird or obtain a copy of Microsoft Office 2010 to get Outlook, although I'd recommend Thunderbird. Likely, WLM has corrupted itself.

No, not shifting the blame from the ISP, just a general recommendation. Could be that they use some other settings for Win Vista/7 machines? Hard to say from here.

FWIW:
some ISP's won't pass port 25 except to their smtp servers so many email programs have a setting for smtp
port. I set most of mine to either 587 or 2525 which works in most cases.

Rich