I see the "Split Group" extension isn't available anymore. I have a group that I am mailing to that has 74,000 emails. My team would like to split this into 2 mailing lists due to how long it takes us to send this many emails. Any ideas?
Simplest is just to do an A/B test, set both to 50% of the total and then pause the second one and restart it whenever you want.
If you really need to split the group, I use SearchKit to create two smart groups, both with members of whatever group you want the email to go to, then also one with Email (Primary) matches pattern something like
^[AC457JMSOWZL] and the other doesn't match pattern with the same pattern. This is a regular expression that matches any email that starts with one of those characters, so you can adjust the exact pattern to get closer to half, but that's fairly close on our list.
Bit awkward, but it works. Using the email to split the list should avoid double-emailing issues if you have two contacts who share an email, so they won't end up in different groups. You can also exclude the first mailing recipients from the second one, just as a belt and braces approach to make sure you aren't emailing anyone twice.
If it's just the time of day when these are delivered that's the issue, you can also send the mailing and just pause it and restart the next day or whatever you want to do.