Thanks Vince, but it is simply "dolphinusers@xxxxxxxxxxxxxxx" (without the quotes of course). But the first two instances were when I tried to reply to a message on the list and the address would have been inserted from the header of the incoming message. All very strange, but I am just about to study the web page which Barry suggested and perhaps an explanation will emerge from this. Douglas On 28 Jun 2006 at 22:53, Vince Thacker wrote: > Douglas, can you quote the exact address you're trying to send to? There > may be a clue in there somewhere. Vince. ----- Original Message ----- > From: "Douglas Harrison" <harrison1d@xxxxxxxxxxxxxx> To: > <access-uk@xxxxxxxxxxxxx> Sent: Wednesday, June 28, 2006 8:33 PM > Subject: > [access-uk] Mail delivery failure > > > >I realise that this is perhaps inappropriate for a Freelists group, > > but I thought that someone might be able to throw light on a problem I > > have experienced for the last 24 hours. > > > > Each time I try to post to a Yahoo groups list of which I am a member I > > get a Mail Delivery Failure message including the following - > > > > "Delivery has failed on the enclosed message for the following > > reasons reported either by the mail delivery system on the mail > > relay host or by the local TCP/IP transport module: > > > > 501 <dolphinusers@xxxxxxxxxxxxxxx boundary=>: malformed address: > > boundary=> may not follow <dolphinusers@xxxxxxxxxxxxxxx > > > > > > I am still receiving mail from the list in question but cannot post to > > it. > > > > Any ideas as to what Error 501 is would be very much appreciated. > > > > Douglas > > > -- Douglas Harrison ** To leave the list, click on the immediately-following link:- ** [mailto:access-uk-request@xxxxxxxxxxxxx?subject=unsubscribe] ** If this link doesn't work then send a message to: ** access-uk-request@xxxxxxxxxxxxx ** and in the Subject line type ** unsubscribe ** For other list commands such as vacation mode, click on the ** immediately-following link:- ** [mailto:access-uk-request@xxxxxxxxxxxxx?subject=faq] ** or send a message, to ** access-uk-request@xxxxxxxxxxxxx with the Subject:- faq