Mail Can't Send To "NULL"

I recently re-indexed and re-built Mail which corrected some problems, but now it seems this "Can't Send From 'Null'" problem is getting worse. Now Mail gets to a point where it won't send no matter how many times I try to re-send. I have to quit Mail. When I re-open, the e-mail generally sends on the first try. However, in short order I am back to the "Null" message and multiple attempts and usually be the end of a day it stops sending altogether again. Anybody got any ideas?

Yes, I did all of that from the MacBook DVD (10.4.6) Disk Utility as well as from the 10.4.11 Disk Utility feature off my active hard drive. Neither discovered any problems. I did it before and after re-indexing and re-building the mailbox files. Thanks for clarifying.

Again many thanks for the advice. However, my port settings are specified by my ISP and none of them are set to 25. smtp.att.yahoo.com uses port 465 with SSL, in Los Angeles anyway.

Also, since I have no SMTP server named "NULL" I can't delete it as indicated in the linked article.

Looks like I will have to delete all of my servers and start from scratch. Not an enviable task. Way to go Apple!

I deleted all of my servers, quit mail, repaired permissions, zapped the pram, restarted the mac, repaired permissions again, confirmed mail settings with only one the one SMTP server. Tried to send mail and got the same "Cannot send to 'NULL'" message. This is ridiculous. Nothing in Apple's support covers this problem from which I cannot recover. All of my settings are correct as I can send and receive from my iPhone just fine.

What now?

SerialPort-2
SerialPort-1
Bluetooth
Built-in Ethernet
Built-in Firewire
AirPort

All are On

Not really interested in doing a complete install. I really shouldn't have to. I don't do anything freaky with my Mac, I simply follow Apple's instructions, buy their products, update my disk with Software Update and mainly use only Apple software. I should not be having these kinds of problems.

Us there anyway just to reinstall Mail? Can I download Mail from Apple and just re-install it?

BDAqua, thanks for your help in going through the steps. I wish something you came up with worked and clearly this is not your problem, but these kinds of ridiculous problems really shouldn't happen. My time on this forum and real-life experiences with friends and family have demonstrated over and over that Mail is a bug-ridden application that works inconsistently at best for almost everyone I know using it and periodically craps out for no reason whatsoever, that is when the ISPs aren't crapping out themselves, in particular Apple's partner ATT using Yahoo.

Yeah, unfortunately it won't send on any of the servers I have with the same "NULL" message error, when I switch to a different one from the drop down menu you reference. What I generally do is to keep hitting "Edit" then "SEND" until it decides it wants to send. Sometimes, it won't send no matter how many times I try, or save and restart. Other times, it goes after the first attempt or second. There is nothing consistent about this problem except the reported cause: "Can't send from server 'NULL'.

Interesting. I re-ordered them. Who knew. I'll report back.

Lately, it's been hit or miss for no rhyme or reason. From the same account sometimes, I have to hit send 5 times and others it goes the first or second try. Occasionally, it will never go. Again, nothing changes within a single e-mail session other than sending and receiving e-mail. Most frustrating.

Hi NOT at all helpful. There is absolutely no rhyme or reason to how many times it takes something to send. After following all the advice given above, nothing has changed. Using the same e-mail account I can send three e-mails in a row, the first one might go immediately, the second might take 5 times and the third might go immediately or take 5 times as well and three more might send in the exact opposite pattern. If I were over my monthly ISP bandwidth, it wouldn't go at all. Further the problem has been continuous for the past 2 months, without a drop when the bandwidth would have reset. As I stated above, my iPhone is not affected at all using the same accounts.