Carefully check the address you are using it probably has some typo.

sherlockiantwo said

i was trying to send my brother e mails but are coming back as undeliverable. If he sends me one and i reply to it ...it goes through ok. I can send e mails to other folks with no problems. have called and talked to him and we can't seem to find out why this problem is occurring. I can go up to googlemail and send him and e mail and it goes through ok comes back undeliverable only using thunderbird. help

John99 said

Carefully check the address you are using it probably has some typo.

sherlockiantwo said

i was trying to send my brother e mails but are coming back as undeliverable. If he sends me one and i reply to it ...it goes through ok. I can send e mails to other folks with no problems. have called and talked to him and we can't seem to find out why this problem is occurring. I can go up to googlemail and send him and e mail and it goes through ok comes back undeliverable only using thunderbird. help

made sure of that John just found out it does this for my brothers e mail and my sister in law (same household) have triple checked what addresses i am sending it to. they are correct. but thanks

In fact just did a copy and paste so after about 25 tries it keeps happening

What is the return message that comes back? It should have a reason code with it.

It says : The error that the other server returned was: 521 5.2.1 : (HVU:B2) http://postmaster.info.aol.com/errors/554hvub2.html

If you look at the info for HVU:B2 it states that there have been complaints about your or your ISPs IP address and it is blocked. Talk to your ISP to get it cleared up so you can send to AOL addresses.

Not sure how to contact my ISP (I have a mac does that change anything) and rarely send my brother an e mail (and he says he hasn't complained) in fact being 68 I rarely use e mail etc. but anyway, this gives me a good start. but, sounds dumb....how do i contact my "isp" thanks so much

There is a link to Support Request in the AOL page you show in the error message. That is why those error messages are included. To help you resolve your problem.