Thanks. I called my provider and verified all my settings but still messages leave very slowly every now and then, especially at the beginning of the day when I turn on my computer (I don't leave it on all the time) or when I haven't sent a message in an hour or so. I use the same provider as in my last place and had no problem there. And I have deleted saved sent addresses. I use Apple wifi with a modem connected to a phone jack on the wall. I noticed that a telephone won't work with the jack but the modem seems to. Is there a chance that the jack is faulty and this is causing the slow smtp sends?
My provider checked my line speeds and they are the same, but I haven't had them checked since moving the modem to a different and perhaps faulty phone jack. I don't have trouble using the Internet with browsers, just MacMail.
I use DSL.
Even one word "test" messages can take several seconds to leave MacMail.
I use a MacBook 4,1 with OS 10.6.8 and Mail 4.6 (1085)
No IPv6 is listed
DNS server is 10.0.1.1
Do you still suggest I change the DNS server to 18.104.22.168?
10.0.1.1 is your router - you may be able to set your DNS server at the router but I understand that often DSL routers (unlike ADSL ones) do not allow you to do this. For the time being I advise setting it to 22.214.171.124 on your Mac. This is a fast Google public DNS server. Simply changing it will clear your DNS cache. You can always change it back or leave it blank to let your router's DHCP server apply it automatically at boot.
Your router would normally use your ISP's DNS server which should, in theory, be your fastest option but in some cases it is faster to use a good public DNS server.