On the account pane, select the button 'manage identities.' Here you can enter an id (and sig if desired) for every alias. Then, when composing a message, the aliases can be selected from the FROM dropdown menu.

Thank you for the prompt reply but I don't think I am grasping it. I currently have 467 of these aliases (forwarding addresses) and was quite pleased with myself for having managed to export them from my domain provider's email interface into a csv file and then put them into my TB address book thinking that would enable TB to "autocomplete" then whenever I started typing one of them in the "customise address field". No such luck - whether it's the first or 50th time I've used them. I don't quite see how the solution works, if it means entering each one individually and then once that task is done, using a drop down menu with 467 aliases to choose from as that involves more work than just tying the whole alias in the "customise from field" box.

When using unique disposable forwarding aliases in the way I do, it is normal to end up with a LOT - one for every organisation/institution/website that you communicate with, as it is a great way of controlling spam and detecting and limiting the damage from the regular data breaches that institutions subject us to nowadays.

What puzzles me is the fact that TB can do autocomplete on all these aliases if I put them in the other fields, such as To, Cc, or Bcc. So the issue is that it will ONLY offer addresses for autocomplete if they are already associated with TB identities. I already have three TB identities associated with pop3/smtp mail accounts and they are all available to choose in a drop down for the From: field. Interestingly, if I start to type one of the existing ID addresses into that "customise From" box, then there is no autocomplete offered on that either - even though it is already on the drop down list for selection.

It looks as if TB is designed NOT to do what I want - there is no autocomplete facility on that "customise From: address" field, even though it allows me to customise a From address, and use it, for some reason it isn't programmed to use the autocomplete function when doing so.

Your solution states: "Here you can enter an id (and sig if desired) for every alias" ? In the manage identities window it looks like you are suggesting I manually create 467 new identities, one for each alias? That's not an attractive solution!

Sorry to sound so negative! Is there any way round this other than creating a new identity for each new forwarding address? If I've misunderstood, my apologies and thanks again for the response.

I understand your frustration, but the FROM field in the compose window is intended to reflect legitimate accounts that are compliant with requirements of email servers. Your approach to controlling SPAM is unusual, and appears to be a lot of work to avoid possible SPAM. Thunderbird's solution does do what you want; the issue is that the entries must be in the 'manage identities' component, not the addressbook.

The "unique disposable address" system is a perfectly legitimate one that has been available from the operators/providers of mail servers for many years now. Yahoo! have operated it for over a decade, and BTInternet offered it via BTYahoo! email when I used to be one of their reluctant customers. My current domain host/email provider, IONOS, offers the sytem. It's not unusual, it's legitimate, - it's a mass market product.

Out of interest, I just resurrected MSOutlook 2007 and tried this, using that - it's what I used to use before switching to Open Source. It can handle entering the disposab le address in the From field, sending the email and autocompleting the address just fine. I'm discouraged that TB can't. But thanks for the help. It is appreciated.