I've used a lot of mail systems over the years with the bulk of my working experience being in IBM Notes. In 2017 we migrated to Outlook but fortunately it's on Office 365 (so I've never had to run an exchange server in the office). These days I spend most of my work mail time in Outlook 365 for the web (and my home mail time in Gmail). As pretty much everyone does, I have a love/hate relationship with email. It's still the number one communications system but there are plenty of alternatives and I'm finding myself using those more and more.
Updated 2025
Gmail is my go-to email system for personal use. It's great and does everything I need for now.
Gmail also has a great mobile version. It's fast and it's powerful.
Outlook is the system I love to hate. I have only started to use the desktop version since 2023 when new outlook made its debut. Everyone else in my company seems to hate it but "new-Outlook" is the first version I've liked.
If there was anything I didn't like about Notes, it was mail. I still use the Notes address book all the time because of group nesting and security but I almost never use the mail these days except to redirect mail elsewhere. Verse was great though.
I've used so many alternatives over the years including Yahoo and Thunderbird and various mini-computer mail systems. I've also used a lot of general utilities, such as MailChimp.
There's quite a few alternatives to mail but these are my favourites;
SharePoint and OneDrive: These days we do the bulk of our internal sharing and collaboration using the Share features of OneDrive and SharePoint. We use these features less often with externals but expect that as more people come onto Office 365 that will change.
Microsoft Teams: Teams is our go-to application for meetings these days and COVID-19 has reinforced that. It's become so much easier to get an instant response via teams than via email and collaborating with others on projects using the file and add-in features keeps on getting better and better.
Google: If it's not work and I'm collaborating with friends and family then Google is my main suite. I share directly using Google Drive or if it's a photo, Google photos.
One of the biggest migrations we did was from Notes to Outlook back in 2017.
The software that worked best for us back then was Stellar (which had a lot of configuration troubles but was faster overall) and Kernel, which was easier to set up but took twice the time. Neither was free.
Migrating Mail from Notes and Verse to Outlook - Part 1 - (April 2017)
Migrating Mail from Notes and Verse to Outlook - Part 2 - (April 2017)
I've also used a number of mail services over the years for marketing and alert purposes. Two which stick in my mind are;
MailChimp - Which is an excellent marketing platform.
MessageMedia - Which allows you to email directly to SMS from various systems. It's great for setting up alerts.