My email is broken – how to diagnose and fix mail problems

Mail's Advanced settings for a typical POP and SMTP service.

Cannot send and/or receive messages

The most common problems with email are failure to receive or send messages. Your first step in either case is to look at the error message, which should give you a good clue as to what went wrong, and may enable you to skip some steps in the process below.

Check and prove connection

If your Mac was unable to make any sort of connection with a remote mail server, next establish that your network and Internet connections are operating normally. Then, if you have another means of connecting to your mail service, do so to check that the servers are running correctly. Try first using the same Internet connection as your Mac. If that does not work, and you have another means such as mobile phone access, try that as well.

Sometimes Internet failures are partial and affect certain services, leaving others such as HTTP for the web unaffected. It is also possible, for example, that the Domain Name Service (DNS) was unable to locate the mail server, in which case you will need to discover why that is – perhaps your DNS settings have become changed, or the DNS you have set is currently unavailable.

Once you are happy that the mail servers are all OK and your connection to them is good, restart your Mac and try again. If you have recently installed new or updated third party software, you might make that a ‘Safe boot’ to eliminate the risk that third-party extensions are the cause.

Check settings

Internet Accounts pane, new to recent versions of OS X, provides system-wide mail settings, but many mail clients do not use those settings.
Internet Accounts pane, new to recent versions of OS X, provides system-wide mail settings, but many mail clients do not use those settings.

If this does not fix the problem, or the connection to the mail server started but then failed, you need to check through all your settings thoroughly to see what is incorrect or changed. This includes:

  • the Internet Accounts pane in System Preferences for that particular service,
  • Mail’s list of SMTP servers if you are using Mail and the problem occurred when trying to send an outgoing message,
  • the other settings for that mail account in the mail client that you are using.
Mail's SMTP server settings for Apple's iCloud service.
Mail’s SMTP server settings for Apple’s iCloud service.

Now that OS X distributes these settings across these different locations, failure in one can be fatal to the whole. This inevitably makes diagnosis more tricky, but Mail comes with some tools to help. The first is the Activity window (opened from the Window menu), which shows progress in making and completing connections. I leave mine open all the time, just in case there is a glitch.

Mail's basic account settings for iCloud IMAP services.
Mail’s basic account settings for iCloud IMAP services.

Check client-server dialogue

Next is the Connection Doctor window, which polls the various servers that you have configured, and gives suggestions as to what may be causing problems with any to which it cannot connect.

The Connection Doctor in Mail is a good way of trying to work out what is wrong with a mail system.
The Connection Doctor in Mail is a good way of trying to work out what is wrong with a mail system.

In theory, if you get a green light on the services in Connection Doctor, the client end should work fine. In practice it may not be quite as simple or crisp. The Connection Doctor also allows you to turn verbose logging on so that you can review the conversations or dialogues which are taking place between Mail and the server, using Console to view the relevant logs. This is a slightly clumsy way to achieve this, but can be well worth the effort. Other mail clients usually provide similar functionality.

When you have obtained a transcript of the dialogue which failed, you will then need to refer to further information to interpret it, and work out what needs fixing. There are full details of each of the major mail protocols, with sample transcripts of client-server dialogues, at:

  • POP, for collecting incoming mail intermittently,
  • SMTP, for sending outgoing mail intermittently,
  • IMAP, for intermittent or continuous collection of incoming mail.

If you are really stuck, you may need to refer to the RFC (the Internet standard document) which contains further example dialogues. Those are available via those Wikipedia articles.

Most connection problems result from incorrect settings and protocols. Sometimes these are temporary glitches at the server end – I have known major mail service providers suddenly change their SMTP authentication for a few hours, and then revert to normal, for example.

Advanced settings for a POP and SMTP service in a third-party mail client.
Advanced settings for a POP and SMTP service in a third-party mail client.

It is more likely that your mail service provider has made an intentional change in the server details, ports used, or authentication method. They should have updated their support pages, but sometimes those lag, and you will need either to try out different alternatives until you find the correct one, or ask them to provide details. I am sorry to say that it is often quicker and simpler to do the former.

Stuck messages

There are a host of other lesser but often infuriating problems that can arise with email. Sometimes empty, corrupt, or vast messages get stuck on your server, and every time that the client tries to download them, the process halts, blocking your incoming mail. That may require the offending message to be deleted from the server, something which will need the assistance of the help desk (and ample time and patience).

Strange mailbox behaviour

Sometimes mailboxes become wobbly, usually when they have grown to astronomical size, or have malformed contents. This is a good time to use the Rebuild command in Mail’s Mailbox menu. However before you try that, you should ensure that you have a current backup of your Mail folder and all its contents, just in case the rebuild makes the problem worse. At least you can then move important messages back into the rebuilt mailbox, if required.

Protocol glitches

You will also discover that not all implementations of the different services are alike. Google’s mail service, for instance, provides an enhanced version of IMAP which has caused compatibility problems with Mail and some other clients. Key to this seems to be Gmail’s All Mail setting: if Show in IMAP is checked, then try unchecking it; if it is unchecked, try checking it. This is detailed here, with some dissenting voices and alternative suggestions in the comments.

Different mail client

If you cannot get Mail or another mail client to do what you want it to, there is no shortage of alternatives. My all-time favourite is the ancient Mailsmith, which is simple to set up but lacks IMAP support. Its great strength is that it only works with text in messages, so that you can see through spam and scam links with the greatest of ease. A trip to the Mac App Store should give you a long list of other potential replacements.

If you are concerned at moving large mailboxes to a new mail client, look first at Emailchemy, which seems able to cope with almost any conversion. However many apps now work with native Mail format, which is a widely-used standard (for once).

Different mail service

Sometimes mail service providers seem unable to solve problems which make your life a misery. There is no shortage of providers, and you may be better off with a different one, whose service works better with Macs. Although tedious to change your address, sometimes it is the best way forward.