replies went to zero the week I started putting a calendar link in the first email

Two separate things happen when you add a link and they compound.

The human one: a calendar link in a first email moves the ask from "reply with a sentence" to "commit thirty minutes of your week to a stranger". That is an enormous jump in cost for someone who has known you for nine seconds. Replies were the cheap action and you removed it.

The machine one: a first-contact email from a domain with little sending history that contains an external link looks materially more like bulk mail than the same email without one. You may not have gone to spam exactly, but landing in the promotions pile or being delayed is enough to flatten a hundred-email sample.

Go back to asking a question. "Is this something you deal with, or am I miles off?" gets a yes or a no, and both are useful.

Numbers side. Eleven replies from a hundred hand-picked emails is a good rate for personalised outreach and you should protect it rather than optimise it. Sending from a normal mailbox, twenty to thirty a day is a sensible ceiling for cold sends regardless of what your provider technically allows, because the provider limits are designed for people emailing colleagues.

The volume rules that get talked about publicly kick in for senders doing thousands a day to one provider, but the underlying signals apply to everyone: authenticate properly, keep complaints near zero, make it trivially easy to be left alone. At your scale complaint rate is the thing that will kill you and it takes very few annoyed recipients to do it.

Check whether your sending tool inserted anything else when you added the link. Several of them turn on click tracking automatically, which rewrites your nice clean link into a redirect through a shared tracking domain. That shared domain has a reputation you do not control and did not earn, and it is exactly the sort of thing that quietly moves you out of the inbox.

If you must track clicks, use a subdomain of your own domain for it. Otherwise turn tracking off entirely on cold sends. You do not need open rates that badly.

Politely, I do not believe the link is the whole story and neither should you. A hundred emails is not a sample, it is an anecdote — eleven replies versus one could be the link, or it could be that your second hundred were further down a list you sorted by how well you knew them, or that they went out in a different week.

Before you rewrite everything, check the boring stuff. Are the second hundred in the same segment? Did you send from the same address? Did anything change in your sending setup between the two batches? Then run fifty with the link and fifty without in the same week, alternating, and look again.

Just went through this and the fix that worked for me was embarrassingly small. I removed the link, removed the logo from my signature, removed the tracking, and made the email look exactly like an email I would send a colleague. Four lines, plain text, one question mark. Replies came back immediately.

The other thing I changed: the second email in the sequence is the one with the calendar link now, and only if they replied. Nobody has complained about a link in a conversation they started.

First email asks a question. Second email, after a reply, offers times. Never send a link to someone who has not spoken to you. This has been true for as long as I have been doing it and no tool has changed it.