advice Which is the best day to send Domain Sales Letter to end-users?

Obviously it depends on their time zone. That is during office hours.
However, for sending spam there is not best day and time, cause it's never welcome.

I've had the most success at 5-6 AM on Wednesday in the recipient's timezone.

For most business people, that guarantees your email will be one of the first they see in the morning when they're fresh and full of energy. Once they start feeling lethargic by the end of the day, they may not feel like responding.

Wednesday is in the middle of most workweeks, and that's good. In the beginning of the week, people are scrambling to catch up on work that accumulated over the weekend. By the end of the week, people are scrambling to finish everything before the weekend.

Payday!

Sorry, couldn't resist...

@Addison's reply sounds really good though...

Morning coffee time..the best!

It's never a good time. like I tell them already if I wanted the name I would own it already.

Hmm.....great suggestions everyone! Keep them coming!

Monday morning their time.

Yes but not 9AM. More like 11AM. Because they need to process all the E-mail from the week-end, plus the junk too Give them some time to clean up their inbox before so they won't trash you out.

Generally most domainers say broadcasting on Thursday/ Friday helps.

Best night time call when they have finished dinner and having few drinks after 9.30pm......

No such thing as a best time IMO, if interested they will reply.

Monday is a lot of hustle and bustle and your email may be seen and then totally forgotten about. Tuesday and Wednesday are much calmer days then most for people to read emails.

Thursday and Friday are the worst days because of the weekend, possibility of an extra long weekend and finishing up that week's tasks. I have had very little success on these days. A lot of people won't even check their email on the weekend and if they get one like this it won't be replied to because they are more concerned about their own time at the moment.

From a pure logical perspective I would say Tuesday and Wednesday would be the best days and it still gives them time to get back to you within the same week.

I read an article about when to send out emails to your list it was written by Salesforce and they claim Thursday. Weekends, Monday and Friday are not good for obvious reasons. They claim 4-5pm local time gets the most replies.

It depends upon the time zone of the buyer find the time you think you buyer wuld be free

sunday

it depends on the time zone of the end user.
it should be sent during the time in which the probability of opening the mail is maximum,for example during the early office time of the end user .