You must use a valid address, or no address. You will notice however that to: like all other addresses is laid out in the form William Gates <Bill@Microsoft.com>, the part in between < and > is the address, but the bit before it is the display name that is used in most occasions to display who the email is addressed to. (Thunderbird by default substitutes the display name you have saved in your address book if the address is in there.)

So if you address the To to yourself, and edit the displayname part in the address line the email will for most people display whatever you set as the display name.

Is there any way to make it only show the name and not the address to all the recipients? I would like them to only see 'hockey team' not 'hockey team<hockey@ mail.com>'

re:If I send an email to 10 people in the BCC field, how can I put a generic name like 'hockey team' in the to: field

I'm wondering to whom are you sending the email which you are putting 'TO field?

If the 'Hockey Team' was a group of 10 people each with their own email address and you wanted to send them all the same email, then you could create a 'Mailing List' called 'Hockey Team' which contained those 10 contacts. Then you would add 'Hocky Team' to the Bcc and only see 'Hockey Team. https://support.mozilla.org/en-US/kb/how-create-and-use-mailing-lists-thunderbird

Equally you could create a Mailing List that only contains your own email address - but it would still be seen by recipient.

But if it is your email address in the TO field and you are entering it to help stop email getting caught by spam filters - then why is it a problem. After all, your email address is already displayed in the FROM.

But no, you cannot send an email address without disclosing it in a TO or Cc field even when sending Yes, you can choose what you see in a received email as described by Matt, but you do not necessarilly have control over what someone else chooses to use as 'Display Name'.

Or you could use an addon called 'Mail Merge' https://addons.thunderbird.net/en-GB/thunderbird/addon/mail-merge/ You use a Template email which you only compose once. You store template email as it makes it easier to reuse.

Create a new address book - not a Mailing List - which holds contacts - all contacts must have valid information in all the fields you use like 'First Name, Last Name, Primary Email' When you use Mail Merge, each email is created separately and email address uses the 'TO field, so you do not need to use Bcc. You use Mail Merge and select to use that particular Address Book. This means you can personalise the email address. No one gets to see any body else's email address. You can include yourself as one of contacts in that address book - handy if you are sending email from one email address , but desire a copy in another email address.

If you want the whole story here it is. I am using the "category manager" addon. When I send to the category all the names go in the BCC field and the category name goes in the TO: field. But Thunderbird errors because of the non email format. I have to delete the TO: field and leave it blank. There are 37 names in one category and I don't want them all exposed to each other.

My previous email program,Eudora, allowed me to nest address names and only put a generic name, like "hockey team" in the to field, no address. I am trying to figure out how to duplicate that function so I don't need to leave the TO: field blank. With the category manager I only have to worry about changing a person's email if they change and not updating a bunch of mail lists also since Thunder won't nest nick names into a mail list. Some people are in multiple categries so that would mean updating multiple mail lists.

Then use a mailing list. It really is that simple. https://support.mozilla.org/en-US/kb/how-create-and-use-mailing-lists-thunderbird

I have no idea how that will play out with your addon, because I have never used it. I see no point in having an addon to do what a mailing list does by default. Send mail to the list.