Back in March I started look­ing for a new mail user agent, com­monly referred to as email client. Dur­ing the last few days I had a lit­tle time at my hands and I tried Claws Mail, eM Client, Post­box and Sylpheed. Regard­ing Post­box I went for the 30-days trial of the full ver­sion after I’ve com­pared the two edi­tions (Post­box and Post­box Express). I set up a few IMAP and POP3 accounts and then I just used each client for a short time.

Once again, I’ll stay true to Thun­der­bird. To be hon­est, I liked Post­box a lot but it’s not that much supe­rior to Thun­der­bird espe­cially if you con­sider the add-ons sit­u­a­tion. What I liked best about Post­box was the way they orga­nized the accounts. That’s where Post­box really shines. So, instead of wast­ing more time with other clients I just went ahead and did what I wanted to do for a few years – I finally cre­ated a nice User.js to store some help­ful pref­er­ences. I thought I’d share a few of the most impor­tant set­tings that I found with you:

// Thunderbird 3 adds a disk cache. Activate it to cache any remote content.
// Messages and attachments are now cached for IMAP accounts as well.
user_pref("browser.cache.disk.enable", true);
// Grant 50 megabytes of storage
user_pref("browser.cache.disk.capacity", 51200);

Now, let’s move on to the IMAP set­tings. Here are some sub­scrip­tion settings:

// check every IMAP folder for new messages
// This way you don't have to subscribe to every folder
user_pref("mail.check_all_imap_folders_for_new", true);
// Automatically subscribe to new folders when they are created (or renamed)
user_pref("mail.imap.auto_subscribe", true);
// Automatically unsubscribe from new folders when they are deleted
// Also, unsubscribe from old names of folders when they are renamed
user_pref("mail.imap.auto_unsubscribe", true);

Now, let’s opti­mize the mail fetch­ing in chunks:

Keep in mind that Google rec­om­mends to turn off fetch­ing mes­sages in chunks for its GMail accounts.

// Fetch the message in chunks
user_pref("mail.imap.fetch_by_chunks", true);
// Maximum chunk size to use when fetching IMAP messages in chunks. Defaults to 10240 bytes.
user_pref("mail.imap.max_chunk_size", 40960);
// Don't fetch the message in chunks unless its at least this size. Defaults to 15360 bytes.
user_pref("mail.imap.min_chunk_size_threshold", 98304);
// Initial chunk size to use when fetching IMAP messages in chunks. Defaults to 10240 bytes.
user_pref("mail.imap.chunk_size", 65536);
// Number of bytes to adjust chunk size by when dynamically adjusting the chunk size. Defaults to 2048 bytes.
user_pref("mail.imap.chunk_add", 8192);
// If a chunk is fetched faster than this, it will increase the chunk size to improve throughput. Defaults to 2 seconds.
user_pref("mail.imap.chunk_fast", 2);
// Ideal amount of time it should take to fetch a chunk. Defaults to 4 seconds.
user_pref("mail.imap.chunk_ideal", 4);

Other IMAP set­tings you may want to consider:

// Download headers for new mail
user_pref("mail.imap.new_mail_get_headers", true);

// Search folder for deleted messages. If none are found the expunge is skipped
user_pref("mail.imap.check_deleted_before_expunge", true);

// Cleanup (expunge) on exit. Messages marked for deletion will be expunged.
user_pref("cleanup_inbox_on_exit", true);
// If you'd rather have them expunged when you delete them in your client uncomment the following line:
// This will also expunge messages marked for deletion after a move operation (moving a msg in a subfolder, for instance)
// user_pref("mail.imap.expunge_after_delete", true);

How to han­dle attach­ments:

// fetch attachments only when needed
user_pref("mail.imap.mime_parts_on_demand", true);
// controls how many leels of nested attachments there has to be before fetching the whole message
user_pref("mail.imap.mime_parts_on_demand_max_depth", 15);
// Always fetch the complete contents of a IMAP message unless its size is greater
// than this value (not worth optimizing whats fetched).
// Defaults to 30000 bytes.
user_pref("mail.imap.mime_parts_on_demand_threshold", 30000);

With these set­tings Thun­der­bird works very well for me. If you have any sug­ges­tions don’t hes­i­tate to comment!