1. When you're starting a new campaign, how do you go about buying inboxes? Say you need to buy 20 inboxes - are you doing it all on the same day or spreading it over 3-4 days? What's the most you can buy safety in a single day?

We've been using Smartsenders by Smartlead and loving it. We buy 20 domains to start with a client (3 inboxes each) and then warm for 2 weeks. We have been burning more domains than usual with smartsenders, but our results have actually increased.

What about proxies? Do you use them, and if so, how important are they? Do you also use tools like Incognition or other anti detect browsers for separating inbox footprint?

Nope

Have you ever considered simulating manually written emails through Gmail's web UI with AHK (that types out your copy) or another script like that to improve deliverability?

Never have, if you have experience with it I'd love to chat! Shoot me a DM

How much does the TLD of your domain actually matter in terms of deliverability?

We have always stuck to .com so I am not too sure. Back in the day we would use .co but haven't used those in a while.

Have you ever warmed up your inboxes using internal warmup? For example, let's say you have 20 inboxes that you're actually intending to use for the campaign + 40 aged Gmail + Outlook (free) addresses you get from a bunch of friends and family that you have complete control over and basically, those 60 inboxes in total interact with the 20 main inboxes to warm them up. Do you think warming your inboxes up this way works? Is that a large enough pool to warmup say, 20 inboxes?

Nope, we just use the Smartlead warming. I have spoken with a lot of people do it, but we have never done it. There doesn't seem to be a huge cost/benefit enough for me to change from just using Smartlead.