Legend
The feature is available. Important restrictions are listed below the icon.
The feature is available, but data may be misrepresented in some rare cases. Details are given below the icon.
The feature is not available.

Calendar Features

Mozilla Thunderbird¹ Microsoft Outlook Android²
Title
Start and end
Time zones
"Local time" is missing, but corresponding events are displayed correctly. Time zones are less fine-grained than in other applications.
"Local time" is missing, but corresponding events are displayed correctly.
Recurrence rules and exceptions
Events repeating on the second-last, third-last or fourth-last weekday of a month are not supported. If a recurrence rule falls on a nonexistent date (i.e. "30. every month" in February), the event may be displayed too often.
Location
Description
Reminders
Reminders after the event's start are not supported. At most one reminder per event.
Attendees
Invitations
Outlook only supports the message store's primary calendar when handling incoming invitations and replies.
Scheduling status
Availability
Priority
Confidentiality
Categories
Attachments
Thunderbird can only attach websites (URLs).
Attachments are not supported, as Outlook does not support attachments outside of the description field.
Features only available within the same application n/a localization preferences for Microsoft applications ("Locale ID"). n/a
Restrictions when using GeneralSync calendars For compatibility reasons, monthly recurrence rules with multiple instances per month and complex imported recurrence rules may get simplified when saving. For compatibility reasons, text formatting and embedded content (images, attachments) within the event description is removed when saving.
For compatibility reasons, recurrence rules for arbitrary week- or weekend-days may get simplified when saving.
Additional internal Outlook fields might not get preserved.
For compatibility reasons, complex recurrence rules may get simplified when importing.

Address Book Features

Mozilla Thunderbird Microsoft Outlook Android²
Name and Nickname
Photo
Chat names
One of each: AIM, Yahoo, Skype, ICQ, XMPP, IRC.
At most one name for each contact. As it is not possible to specify a type, the name will only be visible from Outlook.
Skype, ICQ, XMPP. Additionally at most one SIP-Address per contact.
Email addresses
At most two addresses per contact.
At most three addresses per contact.
Phone numbers
One of each: work, home, fax, pager, mobile.
Two of each: work, home. One of each: mobile, fax, fax (work), fax (home), pager, TTY/TDD, other. As custom fields, one each: Callback, Primary, Radio, Car, Assistant, Company, Telex, ISDN.
work, home, mobile, mobile (work), pager, pager (work), fax, fax (work), fax (home), TTY/TDD, custom, other.
Homepage
One of each: work, home.
One of each: work, home, ftp.
work, home, custom, other.
Postal addresses
One of each: work, home.
One of each: work, home, other.
work, home, custom, other.
Birthday
Incomplete dates (date without year or only the year) are not supported.
Anniversaries
Incomplete dates (date without year or only the year) are not supported. At most one anniversary per contact.
Organizations / Companies
One of each: company name, title, department
One of each: company name, company name (phonetic), title, department, office location, role, identification number
One of each: company name, company name (phonetic), title, department, office location, role
Languages
At most one language per contact.
Relationships
One of each: spouse, referrer, assistant, manager. Any number of times: child.
assistant, child, sweetheart, friend, manager, parent, partner, referrer, kin, spouse, custom.
Gender
Hobbies
Custom fields
4 fields per contact
4 fields per contact
Notes
Confidentiality
Categories
Categories map to "address lists", which do not support contacts without email addresses nor multiple contacts with the same email address.
URL for availability information
x509 certificates
Features only available within the same application preferred message format, Visibility of the contact in email views. chat name (see above), importance, location, name display format, business card design, billing information, customer number, social security number, localization preferences for Microsoft applications ("Locale ID"). favorite contacts.
Restrictions within GeneralSync address books n/a For compatibility reasons, text formatting and embedded content (images, attachments) within the contact's note field is removed when saving.
"Follow up" is not fully supported.
Additional internal Outlook fields might not get preserved.
n/a

These tables refer to the latest version of GeneralSync and its add-ons / add-ins for each individual application.

¹ Calendar features in Mozilla Thunderbird are provided by the add-on "Lightning", which is installed by default.

² GeneralSync provides the listed features to other apps and the operating system. The set of available features also depends on your device and the app you use to access your calendar or contacts.