PolarisMail is an e-mail hosting service based in Montreal, Canada, primarily focused on the value-segment of the market. Founded in 2013, they've maintained impressive uptime statistics and provide a broad feature set comparable to many more mid-priced offerings. Their webmail interface is Group-Office 6.3 and they offer unlimited alias domains and addresses for every subscription.
Pro Typically half the price of brand name e-mail hosting
At $1/month for a 25GiB mailbox and 5GiB of cloud storage, $2.90/month for 50GiB/15GiB of each, and $6/month for a 25GiB ExchangeMail account, that's about half of what you can see for those service levels from Google, Microsoft and Fastmail. Considering the uptime numbers are above industry averages and they don't skimp on security either, that represents some of the best value in the market.
Pro Two factor authentication support
All mailboxes can be setup to use two-factor authentication using a TOTP-based application like Authy, Duo or 1Password. Separately, the Admin Panel features can also be setup to require two factor authentication which is independent of the mailboxes, which adds an extra level of security for the accounts.
Pro Fast POP3/IMAP4/SMTP access
For those that still like to access their e-mail using a bona fide client application like Thunderbird, Outlook or eM Client, there's no limit to the access provided via the standard POP3/IMAP4 servers for incoming mail and a workable limit of 35 e-mails per day sent over the SMTP server, which can be increased by written request. The Autodiscovery feature is still a bit hit-or-miss, so don't be surprised if you have to configure the client with the actual server addresses and ports yourself.
Pro Supports large file attachments (≤ 50MiB)
You can attach large files to your e-mails without a problem, so long as none are larger than 50MiB individually. For files larger than that, it's pretty easy to use the cloud storage to host the file and generate a link to share with someone via e-mail for them to get access to it.
Pro No ads anywhere
From the webmail interface to the groupware, support wiki and company website, there is not a single advertisement to be seen anywhere, on any of them. Their absence is actually pretty jarring if you're used to using the Gmail, Outlook and Yahoo! webmails, just to name a few. Their portals load fast because of it.
Pro Adjustable spam/virus filtering
The Admin Panel lets you select a value on a ten-point scale to determine how permissive or restrictive you want the spam filtering engine (in this case Rspamd, with SpamAssassin running as a secondary trap) to be on each account. It takes a bit of trial-and-error to find the correct number for each account, but works remarkably well after that, though some senders need to be whitelisted manually if they don't conform to good DMARC practices.
Pro Free e-mail migration
Most of the time you can handle this on your own since IMAP4 has been the de facto e-mail standard for so long, but some hosters don't implement it correctly and others like Google specifically mangle it to discourage you from leaving them. In the event you can't get it sorted on your own, Polaris will untangle it for you without a charge if you pay up for at least a year in advance.
Pro Free API access to Admin Panel controls
If you host a lot of e-mail accounts with them, you may want to automate their management behind a CLI or REPL, or if you're getting into the e-mail reselling game then you'll want to map their control panel behind a branded one of your own. Luckily, access to their API is free and moderately well-documented, so all of that is limited only by your imagination.
Pro Message delivery rules
It's easy to write rules to send messages that meet some criteria, say those from a certain e-mail address or domain, or those sent to one of the mailboxes aliases, to bypass the Inbox and be delivered directly to a specific mailbox folder or even just logged and deleted.
Pro 30 day backups
Automatic backups are made of your account (including deleted items) and stored for 30 days, in the event something happens to their equipment or you suddenly realize two weeks after the fact that the e-mail receipt you deleted without thinking is actually needed for something important. They can be restored at will from the Admin Panel, just be sure to export all of the e-mails you've received since then so you can reimport them one the backup restoration process has finished.