When I use Outlook with my POP3 mail with my Verizon ISP, I have a couple of options under "Voting and Tracking Options."

When I check "Request a read receipt for this message," I know that the recipent can block this at the server level, at the computer level or on an optional basis and in those cases, I will receive nothing.

When I check "Request a delivery receipt for this message," however (as I did with a message a few moments ago), within two minutes I generally get back an e-mail from my ISP's Postmaster with the subject, "Delivery Notification: Message successfully relayed" that confirms the e-mail at least got to the other party's server.

Recently I have had a couple of strange things happen to me:

Two e-mails sent to a lawyer at a corporate legal department returned neither receipt. He confirmed for me by telephone that he had received the e-mails but said he had no idea about the delivery receipts.

This week I sent an e-mail to an executive at a different company and have received no receipts of either kind.

Is anyone familiar with this problem? Can ISPs or servers block my ISP from sending me a delivery receipt? (If so, how?)

If this is the case, is there any way to know for sure that your e-mail is getting to the address you specify in the "TO:" line?